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Time of Implantation of the Conceptus and Loss of Pregnancy
Abstract
Implantation of the conceptus is a key step in pregnancy, but little is known about the time of implantation or the relation between the time of implantation and the outcome of pregnancy.
We collected daily urine samples for up to six months from 221 women attempting to conceive after ceasing to use contraception. Ovulation was identified on the basis of the ratio of urinary estrogen metabolites to progesterone metabolites, which changes rapidly with luteinization of the ovarian follicle. The time of implantation was defined by the appearance of chorionic gonadotropin in maternal urine.
There were 199 conceptions, for 95 percent of which (189) we had sufficient data for analysis. Of these 189 pregnancies, 141 (75 percent) lasted at least six weeks past the last menstrual period, and the remaining 48 pregnancies (25 percent) ended in early loss. Among the pregnancies that lasted six weeks or more, the first appearance of chorionic gonadotropin occurred 6 to 12 days after ovulation; 118 women (84 percent) had implantation on day 8, 9, or 10. The risk of early pregnancy loss increased with later implantation (P<0.001). Among the 102 conceptuses that implanted by the ninth day, 13 percent ended in early loss. This proportion rose to 26 percent with implantation on day 10, to 52 percent on day 11, and to 82 percent after day 11.
In most successful human pregnancies, the conceptus implants 8 to 10 days after ovulation. The risk of early pregnancy loss increases with later implantation.
... Over-the-counter early pregnancy tests are designed to react to the presence of this hormone in urine samples, and several studies have made use of this biomarker to estimate pregnancy loss rates. Estimates of loss occurring from implantation through the subsequent month were about 25% to 30% of implanted concepti in several studies in industrialized populations (Wilcox et al., 1999;Ellish et al., 1996;Zinaman et al., 1996;Wang et al., 2003;van Montfrans et al., 2004). In Bolivian women, 31% of implanted concepti were lost within five weeks of conception (Vitzthum et al., 2006). ...
... The North Carolina Early Pregnancy Study (NCEPS) recruited 11. How It Works: The Biological Mechanisms that Generate Demographic Diversity 221 women who self-collected daily urine samples (subsequently assayed for progesterone and estrogen metabolites and hCG) while attempting to become pregnant naturally (Wilcox et al., 1999). Project REPA (Reproduction and Ecology in Provincía Aroma) collected thrice-weekly saliva (assayed for progesterone) and urine samples (tested for hCG) from 191 menstruating rural Bolivian women in a stable sexual partnership (Vitzthum et al., 2004). ...
Human evolutionary demography is an emerging field blending natural science with social science. This edited volume provides a much-needed, interdisciplinary introduction to the field and highlights cutting-edge research for interested readers and researchers in demography, the evolutionary behavioural sciences, biology, and related disciplines.
By bridging the boundaries between social and biological sciences, the volume stresses the importance of a unified understanding of both in order to grasp past and current demographic patterns. Demographic traits, and traits related to demographic outcomes, including fertility and mortality rates, marriage, parental care, menopause, and cooperative behavior are subject to evolutionary processes. Bringing an understanding of evolution into demography therefore incorporates valuable insights into this field; just as knowledge of demography is key to understanding evolutionary processes. By asking questions about old patterns from a new perspective, the volume—composed of contributions from established and early-career academics—demonstrates that a combination of social science research and evolutionary theory offers holistic understandings and approaches that benefit both fields.
Human Evolutionary Demography introduces an emerging field in an accessible style. It is suitable for graduate courses in demography, as well as upper-level undergraduates. Its range of research is sure to be of interest to academics working on demographic topics (anthropologists, sociologists, demographers), natural scientists working on evolutionary processes, and disciplines which cross-cut natural and social science, such as evolutionary psychology, human behavioral ecology, cultural evolution, and evolutionary medicine. As an accessible introduction, it should interest readers whether or not they are currently familiar with human evolutionary demography.
... There is a hypothesis that the endometrium has "window of implantation," a period of time when the endometrium is suitable for implantation [1,2]. ...
... According to this hypothesis [1,2], if the window of implantation and the time of implantation are misaligned, even if a good embryo is transferred to the uterus, pregnancy will not occur. Unfortunately, however, it is not possible to tell by ultrasound or internal examination whether the window of implantation is open or not. ...
We report a successful case for the clinical efficacy of the endometrial receptivity array (ERA) test for a 32-year-old female patient with refractory infertility. After our careful treatment, the patient gave birth to a male baby (3390 g) in November 2021. To our knowledge, though the clinical efficacy of the ERA test is controversial until March 2024, we think that the age of the patients, the number of IVF cycles, and the racial differences may have an impact on the clinical efficacy of the ERA test.
... Then, progesterone allows stromal proliferation to continue but causes epithelial proliferation to stop, and the uterus becomes conducive for embryo attachment on day four of pregnancy 13,16 . In response to embryo attachment to the uterine epithelium, the underlying stromal cells stop proliferating and differentiate into decidual cells, which permit trophoblast invasion and placentation [17][18][19] . ...
... Our findings may have relevance to early pregnancy loss, in which conception occurs but embryo demise arises before six weeks, the time of implantation in healthy pregnancies. Although the majority of early pregnancy losses (which occur in 30-60% of women) 41 are attributed to chromosomal abnormalities, some occur because of the non-receptive uterus and when the embryo fails to implant 19,42,43 . Our observations of severe subfertility and impaired decidualization in Greb1 KO mice suggest that GREB1 has an essential role in uterine function during early pregnancy. ...
Cellular responses to the steroid hormones, estrogen (E2), and progesterone (P4) are governed by their cognate receptor’s transcriptional output. However, the feed-forward mechanisms that shape cell-type-specific transcriptional fulcrums for steroid receptors are unidentified. Herein, we found that a common feed-forward mechanism between GREB1 and steroid receptors regulates the differential effect of GREB1 on steroid hormones in a physiological or pathological context. In physiological (receptive) endometrium, GREB1 controls P4-responses in uterine stroma, affecting endometrial receptivity and decidualization, while not affecting E2-mediated epithelial proliferation. Of mechanism, progesterone-induced GREB1 physically interacts with the progesterone receptor, acting as a cofactor in a positive feedback mechanism to regulate P4-responsive genes. Conversely, in endometrial pathology (endometriosis), E2-induced GREB1 modulates E2-dependent gene expression to promote the growth of endometriotic lesions in mice. This differential action of GREB1 exerted by a common feed-forward mechanism with steroid receptors advances our understanding of mechanisms that underlie cell- and tissue-specific steroid hormone actions.
... A considerable percentage of human conceptions are lost before birth 1,2 . Consistent data from the last decades have shown 10-40% of all embryos fails to implant and further 10-15% pregnancies are lost after implantation before clinical recognition [1][2][3][4][5][6][7]16,17 . Studies using pre-implantation genetics have shown that chromosomal abnormalities are likely responsible for ≈50% of peri-implantation loss 8, 9 , suggesting that environmental factors might play a role in the loss of pregnancies 10,17 . ...
... The rst days during PID are perhaps the most critical during human development 6,7 . It is estimated that 10-40% of early embryos are lost before or at the time of implantation [3][4][5][6][7]38 . We here show that APAP disrupts embryonic development during this sensitive period of life by inhibiting the cell cycle. ...
It is estimated that 10–40% of all human conceptions fail around implantation¹⁻⁷. Genetics explain ≈ 50% of early embryonic loss, leaving a substantial part of early loss without a known cause8,9. Smoking and alcohol are known risk factors for spontaneous abortion, indicating the importance of the chemical environment during embryonic development¹⁰. Here we show that paracetamol (N-acetyl-para-aminophenol (APAP); otherwise known as acetaminophen), the recommended medication for pregnant people for treatment of mild to moderate pain and fever¹¹ and an environmental pollutant¹²⁻¹⁵, disrupts both mouse and human pre-implantation development. We found that APAP inhibited cell cycle progression, likely through ribonucleotide reductase, resulted in blockage of DNA synthesis across all model systems, and reduced pregnancy outcomes in mouse models. At concentrations found in the reproductive system of women after standard administration, APAP exposure decreased human cleavage stage embryo cell numbers or caused direct embryonic fatality. Similar exposure to human blastocyst stage embryos for 6 h resulted in decreased DNA synthesis as well as morphological changes. Our data demonstrate that a widely used mild analgesic and environmental pollutant might result in embryonic loss and provide a foundation for understanding environmentally caused cell cycle inhibition in other processes during development.
... Some of the normal variation may be attributable to the variation in time from the last menstrual period to the implantation of the embryo. 7,[9][10][11] It is also possible that some pregnancies need a longer time than others to reach maturity and thereby spontaneous onset of labor. Improved precision of the remaining duration of a particular pregnancy is important for the timing of interventions such as induction of labor at postterm. ...
Introduction
Our objective was to study the association of placental size, fetal size, and placental size relative to fetal size (placental to fetal ratio) at gestational week 27 with time to spontaneous delivery.
Material and Methods
We included 100 pregnancies in a follow‐up study from gestational week 27 until spontaneous delivery. Placental and fetal volume (in cm³) were measured at gestational week 27 by magnetic resonance imaging (MRI), and the association of placental to fetal ratio (placental volume/fetal volume) with delivery after spontaneous onset of labor was estimated as hazard ratios (HR) by applying Cox regression models. Pregnancies with deliveries after planned cesarean section or induction of labor provided follow‐up time until these events. An HR lower than 1.0 indicates decreased risk of spontaneous delivery.
Results
Mean placental volume was 532 cm³ (SD 136 cm³) at gestational week 27, and fetal volume was 961 cm³ (SD 112 cm³). This yielded a mean placental to fetal ratio of 0.55 (SD 0.12). The HR of spontaneous delivery decreased with increasing placental to fetal ratio (HR 0.013 (95% CI: 0.001–0.121), Wald statistic 14.704 (p < 0.001)), indicating a longer duration of pregnancy with a higher placental to fetal ratio at gestational week 27. The HR of spontaneous delivery also decreased with increasing placental size, but the association was less prominent than the HR associated with placental to fetal ratio (HR 0.997 [95% CI: 0.995–0.999], Wald statistic 7.638 [p = 0.006]). We estimated no association with fetal size (HR 1.001 [95% CI 0.999–1.003], Wald statistic 1.728 [p = 0.189]).
Conclusions
Our findings suggest that the placental to fetal ratio at gestational week 27 may be an indicator of the remaining duration of pregnancy until the onset of spontaneous labor.
... The successful implantation of embryos requires healthy embryos, endometrial receptivity, and constant interaction at the mother-fetus interface. Endometrial receptivity refers to a state of the endometrium in which the endometrium allows the embryo to adhere to, penetrate, and cause changes in the endometrium stroma leading to implantation [43], and it determines the success of embryo implantation [32]. The hyperphysiological hormone environment resulting from ovarian stimulation is not conducive to the establishment of endometrial receptivity during assisted reproductive technology (ART) [22]. ...
Background
The positive effects of dehydroepiandrosterone (DHEA) on oocyte and embryo quality improvement are often concerned. While the results on DHEA-induced endometrial improvement are controversial.
Objective
To evaluate whether DHEA intervention improved endometrial function and reproductive outcomes during in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles and to thus provide clinical recommendations.
Data sources
PubMed, Cochrane Library, EMBASE and Web of Science from database inception to 31 July 2024, without language restrictions. The references of conference proceedings and websites on clinical trials were manually checked.
Study design
Systematic review and meta-analysis.
Study eligibility criteria
Parallel-controlled randomized controlled trials (RCTs) design; women underwent IVF/ICSI, patients in the experimental group received adminstration with DHEA, whereas the control group received with or without placebo; and the outcomes included reproductive or endometrial function.
Study appraisal and synthesis methods
RCTs evaluating the effects of DHEA on IVF/ICSI outcomes were included. Risk of bias and quality of evidence (QoE) were assessed according to the Cochrane Collaboration’s tool and the Grading of Recommendations Assessment, Development and Evaluation system. Odds ratios (ORs) and mean differences (MDs) with 95% confidence intervals (CIs) were assessed by random-effects or fixed-effects models. Subgroup and meta-regression analyses were used to find sources of heterogeneity. Trial sequential analysis was used to judge the stability of the outcomes. Trial sequential analysis was used in order to control for random errors.
Results
A total of 16 trials included 1973 women. DHEA treatment significantly increased endometrial thickness (MD = 0.93, CI: 0.27 to 1.60; low QoE), which helped improve clinical pregnancy rate (CPR) (OR = 1.34, 95% CI: 1.08 to 1.67; low QoE). DHEA administration also increased the quality of oocyte and embryo [including the number of oocytes retrieved (MD = 0.73, CI: 0.36 to 1.10; low QoE), oocytes fertilized (MD = 0.48, CI: 0.10 to 0.87; low QoE), transferred embryos (MD = 0.27, CI: 0.09 to 0.46; very low QoE), and high-quality embryos (MD = 0.65, CI: 0.27 to 1.03; low QoE)]. Subgroup and meta-regression analyses revealed that heterogeneity might be related to disease type, ovarian stimulation protocol, and addition time of DHEA treatment. There was insufficient evidence to reach a conclusion regarding the live birth rate/ongoing pregnancy rate, miscarriage rate, and MII oocyte number of DHEA. And no severe adverse effects were observed with DHEA administration. Due to the apparent improvemen in the CPR, women with thin endometrium might benefit from DHEA cotreament.
Conclusions
Due to the limited sample size and methodological problems, the QoE was low to very low; hence, the results should be interpreted with caution. The effectiveness of DHEA requires more research before it can be considered for clinical practice.
PROSPERO registration
CRD42023428885.
... This condition is speculated to extend the window of endometrial receptivity (ER), potentially delaying the implantation of compromised embryos (Patel and Lessey, 2011). As supported by Wilcox et al. (1999), evaluating ER differences between women with RPL and healthy individuals could be crucial for identifying those at higher risk. Recent studies on ultrasonographic ER evaluation have mainly highlighted endometrial features crucial for predicting outcomes in assisted reproductive technologies, such as endometrial morphology and Doppler blood flow (Khan et al., 2016;Bahrami et al., 2023;Sharfi et al., 2015). ...
Background
Recurrent pregnancy loss (RPL) poses significant challenges in clinical management due to an unclear etiology in over half the cases. Traditional screening methods, including ultrasonographic evaluation of endometrial receptivity (ER), have been debated for their efficacy in identifying high-risk individuals. Despite the potential of artificial intelligence, notably deep learning (DL), to enhance medical imaging analysis, its application in ER assessment for RPL risk stratification remains underexplored.
Objective
This study aims to leverage DL techniques in the analysis of routine clinical and ultrasound examination data to refine ER assessment within RPL management.
Methods
Employing a retrospective, controlled design, this study included 346 individuals with unexplained RPL and 369 controls to assess ER. Participants were allocated into training (n = 485) and testing (n = 230) datasets for model construction and performance evaluation, respectively. DL techniques were applied to analyze conventional grayscale ultrasound images and clinical data, utilizing a pre-trained ResNet-50 model for imaging analysis and TabNet for tabular data interpretation. The model outputs were calibrated to generate probabilistic scores, representing the risk of RPL. Both comparative analyses and ablation studies were performed using ResNet-50, TabNet, and a combined fusion model. These were evaluated against other state-of-the-art DL and machine learning (ML) models, with the results validated against the testing dataset.
Results
The comparative analysis demonstrated that the ResNet-50 model outperformed other DL architectures, achieving the highest accuracy and the lowest Brier score. Similarly, the TabNet model exceeded the performance of traditional ML models. Ablation studies demonstrated that the fusion model, which integrates both data modalities and is presented through a nomogram, provided the most accurate predictions, with an area under the curve of 0.853. The radiological DL model made a more significant contribution to the overall performance of the fusion model, underscoring its superior predictive capability.
Conclusion
This investigation demonstrates the superiority of a DL-enhanced fusion model that integrates routine ultrasound and clinical data for accurate stratification of RPL risk, offering significant advancements over traditional methods.
... When this coordination collapses, implantation fails or becomes defective and generates adverse ripple effects throughout the course of pregnancy, leading to a poor pregnancy outcome (Cha et al., 2012;Song et al., 2002). The receptive window for implantation is also thought to be transient in humans; implantation past this window can lead to spontaneous miscarriages (Wilcox et al., 1999). In humans, the natural rate of conception per cycle (B30%), and up to 75% of failed pregnancies seem to be due to implantation failure (Norwitz et al., 2001). ...
... This window is primarily defined by a combination regulated by P 4 and E 2 , which includes local cytokines and growth factors, glycoproteins on the surface of cells, adhesion molecules, and proteins of the extracellular matrix [133]. In sows, the implantation window mainly refers to the period from day 12 to day 30 after mating; in cows, it is from day 13 to day 16 of pregnancy; in ewes, it is from day 14 to day 21 of pregnancy; and in fertile human females, it refers to the period approximately 6 to 10 days after ovulation [134][135][136][137][138][139]. In contrast, hCG is a well-recognized molecule with pregnancy-maintaining effects, which can act on the endometrium to regulate its tolerance and also contribute to embryo implantation by mediating immunomodulation. ...
Human chorionic gonadotropin is a glycoprotein hormone produced by human or humanoid syncytiotrophoblasts that differentiate during pregnancy. Due to its superior stability and long-lasting effects compared to luteinizing hormone, it is often used to replace luteinizing hormone to regulate reproductive performance in sows. Human chorionic gonadotropin promotes oocyte maturation, follicle development, and luteinization, thereby increasing conception rates and supporting early embryonic development. In sow reproductive management, the application of human chorionic gonadotropin not only enhances ovulation synchrony but also improves the success rate of embryo implantation by regulating endometrial receptivity and immune mechanisms, significantly enhancing overall reproductive performance. This article primarily reviews the application of human chorionic gonadotropin in sow follicle development, luteal maintenance, and embryo implantation, providing theoretical support for its use in improving reproductive performance in sows.
... Implantation of the conceptus is a critical phase in the establishment of a pregnancy, with most cases of successful human pregnancy implantation occurring 8 to 10 days after ovulation and the risk of early loss rising with late implantation (Wilcox et al. 1999). The intricate embryo-maternal dialogue seems to require precise synchronization and communication between the implanting embryo and a receptive endometrium (Aghajanova et al. 2008). ...
Successful embryo implantation relies on a receptive endometrium and a maternofetal dialogue. Abnormal receptivity is a common cause of implantation failure in assisted reproductive techniques. This study aimed to develop a novel transcriptomic-based diagnostic assay, Adhesio, for assessing endometrial receptivity and guiding personalized embryo transfer. Adhesio was developed based on an initial dataset of 74 endometrial biopsies. Two types of biopsy samples were involved: 45 endometrial biopsies collected during the optimal theoretical window of implantation (WOI) and 29 endometrial biopsies which cells have been cultured with or without an autologous embryo. Microarray analysis was performed to identify differentially expressed genes associated with endometrial receptivity and selected candidate genes were assessed using quantitative real-time polymerase chain reaction (RT-qPCR) on biopsy samples. Statistical analyses were conducted to assess the performance and accuracy of Adhesio. The microarray analysis identified three distinct clusters of endometrial samples with differential gene expression patterns. Cluster 1 exhibited 1717 differentially expressed genes involved in biological processes associated with endometrial receptivity. A specific transcriptomic signature of 60 genes associated with endometrial co-culture was obtained using class prediction approach. Thereafter, an original panel of 10 genes was selected as potential biomarkers for endometrial receptivity based on their expression profiles in both endometrial biopsies and co-cultured cells. This article outlines the methodology employed to develop Adhesio, a test that assesses endometrial receptivity using an original panel of 10 genes. These genes are not only involved during the WOI but are also influenced by the maternal–fetal dialogue.
... It begins in the mid-secretory Tianli Yang and Zhaojuan Hou contributed equally to this work and should be considered co-first authors. phase coinciding with the 7th day after the luteinizing hormone (LH) surge and lasts for 4-5 days [5]. However, the optimal duration of the WOI is relatively short and is approximately 24-48 h in humans [6]. ...
Purpose
To investigate whether personalized embryo transfer (pET) predicted by a modified RNA-sequencing-based endometrial receptivity test (rsERT) model can improve intrauterine pregnancy rate (IPR) in patients with a receptive window of implantation (WOI).
Design
A retrospective pilot study was conducted in the Center for Reproductive Medicine, Central South University, from January 2018 to December 2023. A total of 524 patients with receptive WOI results from rsERT were assigned into two groups based on whether they underwent conventional embryo transfer (conventional ET) or pET. Patients in the conventional ET were matched with those in the pET group at a 1:1 ratio using propensity score matching (PSM).
Results
Before PSM, the IPR (55.73% vs. 46.19%, P = 0.032) and implantation rate (IR) (47.51% vs. 34.03%, P = 0.000) in the pET group were significantly higher than that in the conventional ET group. However, the number and types of transferred embryos differed significantly between the two groups. After adjusting for confounding factors, IPR (57.38% vs. 44.81, P = 0.016) and IR (46.81% vs. 33.10%, P = 0.001) remained significantly higher in the pET group compared to the conventional ET group. The implantation failure rate was significantly lower in the pET group compared to controls (42.62% vs. 55.19%, P = 0.016). Additionally, the multiple-pregnancy rate was significantly higher in the pET group compared to the conventional ET group (10.29% vs. 1.68%, P = 0.001).
Conclusions
Women with receptive WOI results could benefit from the receptivity-timed pET predicted by the newly refined rsERT. These findings provide a basis for future research in precision medicine for embryo transfer.
... Endometriosis and its accompanying inflammation affect endometrial function, leading to progesterone resistance [16][17][18]. The endometrium is a highly dynamic tissue that plays an essential role in establishment of pregnancy, with a window of implantation (WOI) occurring between 6 to 10 days after ovulation [19,20]. These changes, which are referred to collectively as "endometrial receptivity", are complex and arise in response to ovarian steroids and related autocrine and paracrine factors [17,21]. ...
Unexplained euploid embryo transfer failure (UEETF) is a frustrating and unanswered conundrum accounting for 30 to 50% of failures in in vitro fertilization using preimplantation genetic testing for aneuploidy (PGT-A). Endometriosis is thought by many to account for most of such losses and menstrual suppression or surgery prior to the next transfer has been reported to be beneficial. In this study, we performed endometrial biopsy in a subset of women with UEETF, testing for the oncogene BCL6 and the histone deacetylase SIRT1. We compared 205 PGT-A cycles outcomes and provide those results following treatment with GnRH agonist versus controls (no treatment). Based on these and previous promising results, we next performed a pilot randomized controlled trial comparing the orally active GnRH antagonist, elagolix, to oral contraceptive pill (OCP) suppression for 2 months before the next euploid embryo transfer, and monitored inflammation and miRNA expression in blood, before and after treatment. These studies support a role for endometriosis in UEETF and suggest that medical suppression of suspected disease with GnRH antagonist prior to the next transfer could improve success rates and address underlying inflammatory and epigenetic changes associated with UEETF.
... 15,16 The proposed underlying mechanisms are impaired placental development 17 and delayed implantation. 18 Our study findings showed a significant association between very early pregnancy β-hCG concentrations and risk of miscarriage. Therefore, low β-hCG concentrations could be a Type of embryo transfer method may affect pregnancy outcomes in IVF/ICSI cycles. ...
Background
This study aimed to examine maternal serum concentration of β‐human chorionic gonadotropin (β‐hCG) on Day 16 after embryo transfer and risk of miscarriage, pre‐eclampsia, and intrauterine growth restriction (IUGR).
Methods
In this study, we evaluated 125 pregnancies following in vitro fertilization (IVF). β‐hCG concentrations were measured on the morning of Day 16 after embryo transfer. Baseline characteristics of the study participants were also recorded.
Results
Concentrations of β‐hCG on Day 16 after embryo transfer were inversely associated with the higher risk of miscarriage (p < 0.001), but did not with pre‐eclampsia and IUGR (p > 0.05). Spearman's correlation coefficient showed a reverse and significant association between β‐hCG and higher risk of miscarriage (σ = 0.531 and p < 0.001). There was a significant association between frozen embryo transfer and the risk of IUGR and pre‐eclampsia (p = 0.005 and p = 0.023, respectively).
Conclusions
Maternal serum concentrations of β‐hCG on Day 16 after IVF/embryo transfer were associated with the higher risk of miscarriage, but not pre‐eclampsia and IUGR.
... The human endometrium is not receptive to embryonic implantation during most of the menstrual cycle; however, it becomes receptive for a period of 2 to 4 days within the mid-secretory phase of the menstrual cycle known as the window of implantation [1,2]. Therefore, an embryo and endometrium must communicate with one another in synchrony and coordination for implantation to be successful [3]. ...
Purpose
Gene expression analysis of the endometrium has been shown to be a useful approach for identifying the molecular signatures and pathways involved in recurrent implantation failure (RIF). Nevertheless, individual studies have limitations in terms of study design, methodology and analysis to detect minor changes in expression levels or identify novel gene signatures associated with RIF.
Method
To overcome this, we conducted an in silico meta-analysis of nine studies, the systematic collection and integration of gene expression data, utilizing rigorous selection criteria and statistical techniques to ensure the robustness of our findings.
Results
Our meta-analysis successfully unveiled a meta-signature of 49 genes closely associated with RIF. Of these genes, 38 were upregulated and 11 downregulated in RIF patients’ endometrium and believed to participate in key processes like cell differentiation, communication, and adhesion. GADD45A, IGF2, and LIF, known for their roles in implantation, were identified, along with lesser-studied genes like OPRK1, PSIP1, SMCHD1, and SOD2 related to female infertility. Many of these genes are involved in MAPK and PI3K-Akt pathways, indicating their role in inflammation. We also investigated to look for key miRNAs regulating these 49 dysregulated mRNAs as potential diagnostic biomarkers. Along with this, we went to associate protein–protein interactions of 49 genes, and we could recognize one cluster consisting of 11 genes (consisted of 22 nodes and 11 edges) with the highest score (p = 0.001). Finally, we validated some of the genes by qRT-PCR in our samples.
Conclusion
In summary, the meta-signature genes hold promise for improving RIF patient identification and facilitating the development of personalized treatment strategies, illuminating the multifaceted nature of this complex condition.
... Progesterone, produced by the corpus luteum, primes the uterus for implantation (4). The endometrial lining is most receptive to an implanting embryo during a limited period known as the "implantation window, " which typically spans 4 to 6 days during the mid-luteal phase (5). The endometrial tissue undergoes substantial modifications, leading up to this critical phase. ...
The initiation of human pregnancy is marked by the implantation of an embryo into the uterine environment; however, the underlying mechanisms remain largely elusive. To address this knowledge gap, we developed hormone-responsive endometrial organoids (EMO), termed apical-out (AO)–EMO, which emulate the in vivo architecture of endometrial tissue. The AO-EMO comprise an exposed apical epithelium surface, dense stromal cells, and a self-formed endothelial network. When cocultured with human embryonic stem cell–derived blastoids, the three-dimensional feto-maternal assembloid system recapitulates critical implantation stages, including apposition, adhesion, and invasion. Endometrial epithelial cells were subsequently disrupted by syncytial cells, which invade and fuse with endometrial stromal cells. We validated this fusion of syncytiotrophoblasts and stromal cells using human blastocysts. Our model provides a foundation for investigating embryo implantation and feto-maternal interactions, offering valuable insights for advancing reproductive medicine.
Developing a minimally invasive, real-time diagnostic tool to accurately assess endometrial conditions is critical to increasing pregnancy rates in assisted reproductive technology (ART). In this research, fiberoptic bronchoscopy and optical coherence tomography (OCT) were used before and after alcohol injury and human chorionic gonadotropin (hCG)-induced pseudopregnancy to monitor changes in the rabbit endometrium. Histological analysis and electron microscopy were performed on 1 cm uterine sections while simultaneously training a conditional generative adversarial network (cGAN) to convert OCT images into virtual hematoxylin and eosin H&E stained sections. By combining these optical elements, we have managed to non-invasively observe changes in the endometrium at different stages. Traditional endoscopy assesses surface changes such as mucosal color changes, congestion, and fibrous adhesions, while OCT provides detailed views of superficial and submucosal changes and can correspond to pathological H&E sections. Machine learning improves OCT by converting images to H&E format, enabling real-time, non-invasive assessment of endometrial status and improving the accuracy of endometrial receptivity assessment.
Understanding human endometrial dynamics in the establishment of endometrial receptivity remains a challenge, which limits early diagnosis and treatment of endometrial-factor infertility. Here, we decode the endometrial dynamics of fertile women across the window of implantation and characterize the endometrial deficiency in women with recurrent implantation failure. A computational model capable of both temporal prediction and pattern discovery is used to analyze single-cell transcriptomic data from over 220,000 endometrial cells. The time-series atlas highlights a two-stage stromal decidualization process and a gradual transitional process of the luminal epithelial cells across the window of implantation. In addition, a time-varying gene set regulating epithelium receptivity is identified, based on which the recurrent implantation failure endometria are stratified into two classes of deficiencies. Further investigation uncovers a hyper-inflammatory microenvironment for the dysfunctional endometrial epithelial cells of recurrent implantation failure. The holistic characterization of the physiological and pathophysiological window of implantation and a computational tool trained on this temporal atlas provide a platform for future therapeutic developments.
Background
Empirically evaluating the potential impact of recall bias on observed associations of prenatal medication exposure is crucial.
Objective
We sought to assess the effects of exposure misclassification on previous studies of the use of nonsteroidal anti‐inflammatory drugs (NSAIDs) in early pregnancy and increased risk of amniotic band syndrome (ABS).
Methods
Using data from the National Birth Defects Prevention Study (NBDPS) on births from 1997 to 2011, we included 189 mothers of infants with ABS and 11,829 mothers of infants without congenital anomalies. We identified external studies of medication use during pregnancy to obtain validity parameters for a probabilistic bias analysis to adjust for exposure misclassification. Due to uncertainty about the transportability of these parameters, we conducted multidimensional bias analyses to explore combinations of values on the results.
Results
When we assumed higher specificity in cases or higher sensitivity in controls, misclassification‐adjusted estimates suggested confounding‐adjusted estimates were attenuated. However, in a few instances, when we assumed greater sensitivity in the cases than the controls (and Sp ≥ 0.9), the misclassification‐adjusted estimates suggested upward bias in the confounding‐adjusted estimates.
Conclusions
Results from our bias analysis highlighted that the magnitude of bias depended on the mechanism and the extent of misclassification. However, the parameters available from the validation studies were not directly applicable to our study. In the absence of reliable validation studies, considering mechanisms of bias and simulation studies to outline combinations of plausible scenarios to better inform conclusions on the effects of these medications on pregnancy outcomes remains important.
There is limited clinical research investigating the optimal transplantation strategy in early oocyte retrieval cycles. We aimed to assess whether the maturation of oocytes from early oocyte retrieval influenced pregnancy outcomes, and to find the optimal embryo transfer strategy (fresh or frozen-thawed embryo transfers) for patients who had early oocyte retrieval and underwent in vitro maturation (IVM). A retrospective cohort study was conducted in a university-based reproductive medical center. A total of 234 women who underwent single embryo transfer after early oocyte retrieval were included. The primary outcome was live birth rate. The live birth rate (12.5% vs. 27.5%, p = 0.005, adjusted p = 0.010) was significantly lower in IVM cycles compared with no IVM cycles. There was a significant decrease in live birth (3.6% vs. 19.0%, p = 0.008, adjusted p = 0.011) and a markedly elevated early pregnancy loss rate (62.5% vs. 11.1%, p = 0.014, adjusted p = 0.012) for IVM fresh cycles compared with no IVM fresh cycles. However, these findings were not repeated in subgroup analysis when frozen-thaw embryos were transferred. These results indicate that patients who underwent early oocyte retrieval and then IVM-intracytoplasmic sperm injection should be recommended the embryo cryopreservation strategy. Resynchronization of the embryo and the endometrium in frozen-thaw embryo transfer cycles may optimize live birth and decrease early pregnancy loss in IVM-intracytoplasmic sperm injection cycles after early oocyte retrieval.
Uterine dendritic cells (uDCs) are critical for endometrial function, yet their origin, molecular characteristics, and specific roles during the pre- and post-implantation periods in the human endometrium remain largely unknown. The complexity of the endometrial environment makes defining the contributions of uDCs subtypes challenging. We hypothesize that distinct uDC subsets carry out specialized functions, and that resident progenitor DCs generate these subtypes. Employing single-cell RNA sequencing on uterine tissues collected across different menstrual phases and during early pregnancy, we identify several uDCs subtypes, including resident progenitor DCs. CITE-seq was performed on endometrial single-cell suspensions to link surface protein expression with key genes identified by the RNAseq analysis. Our analysis revealed the developmental trajectory of the uDCs along with the distinct functional roles of each uDC subtype, including immune regulation, antigen presentation, and creating a conducive environment for embryo implantation. This study provides a comprehensive characterization of uDCs, serving as a foundational reference for future studies for better understanding female reproductive disorders such as infertility and pregnancy complications.
Background
In recent years, extensive research has been conducted on endometrial receptivity (ER), with rapidly evolving research hotspots and trends. Our study aimed to explore the development of ER research from 2000 to the present and provide insights for future endeavors.
Materials and methods
Relevant research publications on ER from 2000 to 2024 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace, VOSviewer and Excel tools were employed to conduct the bibliometric analysis.
Results
A total of 3,354 articles were analyzed, revealing an overall upward trend in annual publication numbers, signifying the increasing attractiveness and research value of this field. Globally, China led with a notable advantage of 1,030 publications, followed by the United States (650) and Spain (251), constituting the first tier of international research. Valencia University topped the list of institutions with 108 publications, closely followed by Shanghai Jiao Tong University with 87. Fertility and Sterility (IF6.6, Q1) is the one with the largest number of publications, accounting for 7.96% of the total publications. The three most co-cited journals were Fertility and Sterility, Biology of Reproduction, and Human Reproduction. A co-citation reference analysis revealed that ER research can be categorized into ten major subfields, including embryo implantation, frozen embryo transfer, integrins, recurrent implantation failure, intrauterine adhesions, etc. Since 2020, the keywords with the strongest citation bursts include repeated implantation failure and frozen.
Conclusion
This study employs bibliometric analysis to offer researchers in the field of ER a comprehensive perspective. Since 2000, there has been a remarkable surge in the number of publications in the ER research field. These studies primarily concentrate on delving into the pathophysiological mechanisms of ER, with the primary objective of enhancing clinical pregnancy rates and live birth rates, benefiting more infertile patients. Currently, addressing the ER issues in patients with recurrent implantation failure represents the forefront of research. The primary treatment approaches currently in use involve optimizing embryo transfer timing and employing innovative strategies such as immunotherapy. These cutting-edge analyses not only provide new insights into the treatment of ER but also offer researchers fresh research directions, and staying abreast of the latest trends and advancements in the field.
The endometrium undergoes substantial remodeling in each menstrual cycle to become receptive to an implanting embryo. Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. MicroRNA-124-3p is elevated in both the serum and endometrial tissue of women with chronic endometritis, a condition associated with infertility. MicroRNA-124-3p also has a role in cell adhesion, a key function during receptivity to allow blastocysts to adhere and implant. In this study, we aimed to determine the function of microRNA-124-3p on endometrial epithelial adhesive capacity during receptivity and effect on embryo implantation. Using a unique inducible, uterine epithelial-specific microRNA overexpression mouse model, we demonstrated that elevated uterine epithelial microRNA-124-3p impaired endometrial receptivity by altering genes associated with cell adhesion and polarity. This resulted in embryo implantation failure. Similarly in a second mouse model, increasing microRNA-124-3p expression only in mouse uterine surface (luminal) epithelium impaired receptivity and led to implantation failure. In humans, we demonstrated that microRNA-124-3p was abnormally increased in the endometrial epithelium of women with unexplained infertility during the receptive window. MicroRNA-124-3p overexpression in primary human endometrial epithelial cells (HEECs) impaired primary human embryo trophectoderm attachment in a 3-dimensional culture model of endometrium. Reduction of microRNA-124-3p in HEECs from infertile women normalized HEEC adhesive capacity. Overexpression of microRNA-124-3p or knockdown of its direct target IQGAP1 reduced fertile HEEC adhesion and its ability to lose polarity. Collectively, our data highlight that microRNA-124-3p and its protein targets contribute to endometrial receptivity by altering cell polarity and adhesion.
Background
Recurrent pregnancy loss (RPL) frequently links to a prolonged endometrial receptivity (ER) window, leading to the implantation of non-viable embryos. Existing ER assessment methods face challenges in reliability and invasiveness. Radiomics in medical imaging offers a non-invasive solution for ER analysis, but complex, non-linear radiomic-ER relationships in RPL require advanced analysis. Machine learning (ML) provides precision for interpreting these datasets, although research in integrating radiomics with ML for ER evaluation in RPL is limited.
Objective
To develop and validate an ML model that employs radiomic features derived from multimodal transvaginal ultrasound images, focusing on improving ER evaluation in RPL.
Methods
This retrospective, controlled study analyzed data from 346 unexplained RPL patients and 369 controls. The participants were divided into training and testing cohorts for model development and accuracy validation, respectively. Radiomic features derived from grayscale (GS) and shear wave elastography (SWE) images, obtained during the window of implantation, underwent a comprehensive five-step selection process. Five ML classifiers, each trained on either radiomic, clinical, or combined datasets, were trained for RPL risk stratification. The model demonstrating the highest performance in identifying RPL patients was selected for further validation using the testing cohort. The interpretability of this optimal model was augmented by applying Shapley additive explanations (SHAP) analysis.
Results
Analysis of the training cohort (242 RPL, 258 controls) identified nine key radiomic features associated with RPL risk. The extreme gradient boosting (XGBoost) model, combining radiomic and clinical data, demonstrated superior discriminatory ability. This was evidenced by its area under the curve (AUC) score of 0.871, outperforming other ML classifiers. Validation in the testing cohort of 215 subjects (104 RPL, 111 controls) confirmed its accuracy (AUC: 0.844) and consistency. SHAP analysis identified four endometrial SWE features and two GS features, along with clinical variables like age, SAPI, and VI, as key determinants in RPL risk stratification.
Conclusion
Integrating ML with radiomics from multimodal endometrial ultrasound during the WOI effectively identifies RPL patients. The XGBoost model, merging radiomic and clinical data, offers a non-invasive, accurate method for RPL management, significantly enhancing diagnosis and treatment.
Background
The pregnancy stage is known as implantation, when the attachment occurs between the embryo and the uterine wall.
Aim
This study aimed to evaluate the incidence of abortion and the gestational outcome in a low-implanted gestational sac in the first trimester in primigravidae till 28 weeks.
Patients and methods
The observational cohort prospective study was conducted on 100 primigravidae pregnant women with low-lying-implantation pregnancies in the first trimester. When we used the research, we omitted the patient’s name. It was only for scientific purposes that the data from this research was analyzed; it was not utilized for any other purpose.
Results
First-trimester bleeding, it occurred more in cases that had a gestational sac localized 0–0.5 cm from the internal ostium (OS) in 10 cases followed by cases who had a gestational sac localized more than 0.5–1 cm from the internal OS in 12 cases. Twelve cases had an abortion in the first trimester and eight cases had an abortion in the second trimester. Gestational outcome at the 28th week, 74 cases continued to the 28th week of gestation, 20 cases were aborted before the 28th week, and six cases were missed. Mode of delivery: 49 cases had cesarean section and 25 cases had normal delivery.
Conclusions
In primigravidas situations, the low-implanted gestational sac may increase the risk of bleeding depending on the distance from the internal OS, affecting the future position and development of the placenta with no additional risk to maternal and fetal survival.
Background
Accurately predicting ovulation timing is critical for women undergoing natural cycle-frozen embryo transfer. However, the precise predicting of the ovulation timing remains challenging due to the lack of consensus among different clinics regarding the definition of this significant event.
Objective
To compare the effectiveness of preovulatory serum progesterone levels (P4) versus luteinizing hormone levels (LH) in predicting ovulation time using two machine learning models.
Methods
771 patients who underwent autologous natural cycle-frozen embryo transfer between January 2015 and February 2022 were recruited. Utilizing variables including follicle diameters, preovulatory serum levels of LH, E2, and P4, two machine learning models were constructed to predict the ovulation time, the importance of the variables in predicting ovulation timing was further ranked.
Results
Two machine learning models have the capability to accurately predict the timing of ovulation, specifically within 72, 48, or 24 h. The overall accuracy rates of the validation dataset, as determined by the classification trees and random forest models, were found to be 78.83% and 85.28% respectively. Notably, when predicting ovulation within 24 h, the accuracy rate of P4 ≥ 0.65ng/ml exceeded 92%. Furthermore, it was important to consider LH or E2 levels in conjunction with P4 when assessing ovulation timing in cases where P4<0.65ng/ml.
Conclusions
Preovulatory serum P4 levels are better predictors of ovulation timing than LH levels and could be used as an alternative in clinical settings, and the model we developed can be used to pinpoint the day of ovulation. Ongoing research and advancements in technology are anticipated to enhance and refine the ovulation method.
Purpose
The objective of this study was to assess reproductive outcomes of D6 blastocysts transferred on day 6 in comparison to those transferred on day 7 of progesterone exposure in frozen-thawed embryo transfer cycles.
Patients and Methods
This retrospective cohort study included 2029 D6 single blastocysts from the first frozen-thawed embryo transfer cycles of patients at the Hospital for Reproductive Medicine Affiliated to Shandong University from February 2017 to January 2020. Participants were divided into Group A (blastocyst transferred on the 6th day of progesterone exposure, n=1634) and Group B (blastocyst transferred on the 7th day of progesterone exposure, n=395).
Results
The live birth rate was comparable between Group A and Group B (38.7% versus 38.7%, P=0.999). Subgroup analysis revealed a significantly higher preterm birth rate in D6 single blastocysts transferred on the 7th day than in those transferred on the 6th day of progesterone exposure for natural cycle frozen-thawed embryo transfer (5.2% versus 11.3%, P=0.020). After adjustment for potential confounders, the differences in the preterm birth rate in natural cycles persisted (adjusted odds ratio 2.347, 95% confidence interval 1.129–4.877, P=0.022).
Conclusion
In frozen-thawed embryo transfer cycles, transferring on the 6th or 7th day of progesterone exposure of D6 blastocysts did not affect the live birth rate; however, when a natural cycle protocol is adopted, the possible preterm risk of transferring D6 blastocysts on the 7th day of progesterone exposure should be noted.
Study question:
Is there an association between the length of in vitro culture, mode of ART and the initial endogenous hCG rise, in cycles with a foetal heartbeat after single embryo transfer (ET) and implantation?
Summary answer:
Both the length of in vitro culture and the mode of ART have an impact on the initial endogenous rise in hCG in singleton pregnancies.
What is known already:
Different factors have been identified to alter the kinetics of hCG in pregnancies. Current studies show conflicting results regarding the kinetics of hCG after different types of ART (fresh vs frozen ET (FET)), the inclusion or not of preimplantation genetic testing (PGT), and the length of time in in vitro culture.
Study design, size, duration:
This was a multicentre cohort study, using prospectively collected data derived from 4938 women (5524 treatment cycles) undergoing IUI (cycles, n = 608) or ART (cycles, n = 4916) treatments, resulting a in singleton ongoing pregnancy verified by first-trimester ultrasound scan. Data were collected from the Danish Medical Data Centre, used by the three participating Danish public fertility clinics at Copenhagen University hospitals: Herlev Hospital, Hvidovre Hospital, and Rigshospitalet, from January 2014 to December 2021.
Participants/materials, setting, methods:
The fresh ET cycles included cleavage-stage (2 or 3 days in vitro) and blastocyst (5 days in vitro) transfers. FET cycles included cleavage-stage (3 days in vitro before cryopreservation) or blastocyst (5 or 6 days in vitro before cryopreservation) transfers. The IUI cycles represented no time in vitro. To attain a comparable interval for serum-hCG (s-hCG), the ovulation induction time was identical: 35-37 h before oocyte retrieval or IUI. The conception day was considered as: the insemination day for pregnancies conceived after IUI, the oocyte retrieval day for fresh ET, or the transfer day minus 3 or 5 as appropriate for FET of Day 3 or 5 embryos. Multiple linear regression analysis was used, including days post-conception for the hCG measurement as a covariate, and was adjusted for the women's age, the cause of infertility, and the centre. For FET, a sensitivity analysis was used to adjust for endometrial preparation.
Main results and the role of chance:
The study totally includes 5524 cycles: 2395 FET cycles, 2521 fresh ET cycles, and 608 IUI cycles. Regarding the length of in vitro culture, with IUI as reference (for no time in in vitro culture), we found a significantly lower s-hCG in pregnancies achieved after fresh ET (cleavage-stage ET or blastocyst transfer). S-hCG was 18% (95% CI: 13-23%, P < 0.001) lower after fresh cleavage-stage ET, and 23% (95% CI: 18-28%, P < 0.001) lower after fresh blastocyst transfer compared to IUI. In FET cycles, s-hCG was significantly higher after blastocyst transfers compared to cleavage-stage FET, respectively, 26% (95% CI: 13-40%, P < 0.001) higher when cryopreserved on in vitro Day 5, and 14% (95% CI: 2-26%, P = 0.02) higher when cryopreserved on in vitro Day 6 as compared to Day 3. Regarding the ART treatment type, s-hCG after FET blastocyst transfer (Day 5 blastocysts) cycles was significantly higher, 33% (95% CI: 27-45%, P < 0.001), compared to fresh ET (Day 5 blastocyst), while there was no difference between cleavage-stage FET (Days 2 + 3) and fresh ET (Days 2 + 3). S-hCG was 12% (95% CI: 4-19%, 0.005) lower in PGT FET (Day 5 blastocysts) cycles as compared to FET cycles without PGT (Day 5 blastocysts).
Limitations, reasons for caution:
The retrospective design is a limitation which introduces the risk of possible bias and confounders such as embryo score, parity, and ovarian stimulation.
Wider implications of the findings:
This study elucidates how practices in medically assisted reproduction treatment are associated with the hCG kinetics, underlining a potential impact of in vitro culture length and mode of ART on the very early embryo development and implantation. The study provides clinicians knowledge that the type of ART used may be relevant to take into account when evaluating s-hCG for the prognosis of the pregnancy.
Study funding/competing interest(s):
No funding was received for this study. AP has received consulting fees, research grants, or honoraria from the following companies: Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos, Merck A/S, and Organon. AZ has received grants and honoraria from Gedeon Richter. NLF has received grants from Gedeon Richter, Merck A/S, and Cryos. MLG has received honoraria fees or research grants from Gedeon Richter, Merck A/S, and Cooper Surgical. CB has received honoraria from Merck A/S. MB has received research grants and honoraria from IBSA. MPR, KM, and PVS all report no conflicts of interest.
Trial registration number:
The study was registered and approved by the Danish Protection Agency, Capital Region, Denmark (Journal-nr.: 21019857). No approval was required from the regional ethics committee according to Danish law.
Factors affecting embryo implantation, particularly in assisted reproductive technology, remain controversial and poorly understood. Better understanding and optimization of the process of implantation in assisted reproductive technology is important to improving live birth rate and pregnancy outcomes. In this literature review, we examine the key factors involved in implantation and elaborate on current practice, emerging data, and gaps in knowledge.
Despite the association of endometriosis with infertility, the exact reason why endometriosis affects conception and pregnancy establishment remains ambiguous. For successful embryo implantation, a good-quality embryo and optimal endometrial receptivity are required. While the effect of endometriosis on oocyte quality has been demonstrated, the negative effect of endometriosis on uterine receptivity is still under debate. Different pathological processes involving inflammation, immune modulation, aberrant angiogenesis, oxidative stress, extracellular matrix remodelling, and genetic and epigenetic changes together with microbial environment could impact endometrial receptivity and implantation process in women with endometriosis. However, there is no consensus on whether endometrial receptivity is dys-regulated and which molecular mechanisms are involved in women suffering from this chronic disease. This chapter will provide an overview of the available data on endometrial receptivity in endometriosis.
Endometrial receptivity is a gateway to a successful pregnancy. Emerging evidence has proven the crucial role of endometrial receptivity in blastocyst adhesion and embryonic development, yet its establishment and receptivity are not fully understood. The endometrium is a hormonally regulated tissue that is subjected to variations due to a variety of underlying factors. Understanding the molecular basis and genetics behind endometrial receptivity might pave the way to better diagnostics and therapy in infertility management. In this chapter, we will gain insights into the significance of endometrial receptivity in implantation and genetic testing methods to test endometrial receptivity. Special attention is paid to highlight the complexity of endometrial receptivity, the genetic tests employed to predict endometrial receptivity, and the future possibilities for personalized medicine in this area.
Poly- and per-fluoroalkyl substances (PFAS) are synthetic environmentally persistent chemicals. Despite the phaseout of specific PFAS, their inherent stability has resulted in ubiquitous and enduring environmental contamination. PFAS bioaccumulation has been reported globally with omnipresence in most populations wherein they have been associated with a range of negative health effects, including strong associations with increased instances of testicular cancer and reductions in overall semen quality. To elucidate the biological basis of such effects, we employed an acute in vitro exposure model in which the spermatozoa of adult male mice were exposed to a cocktail of PFAS chemicals at environmentally relevant concentrations. We hypothesized that direct PFAS treatment of spermatozoa would induce reactive oxygen species generation and compromise the functional profile and DNA integrity of exposed cells. Despite this, post-exposure functional testing revealed that short-term PFAS exposure (3 h) did not elicit a cytotoxic effect, nor did it overtly influence the functional profile, capacitation rate, or the in vitro fertilization ability of spermatozoa. PFAS treatment of spermatozoa did, however, result in a significant delay in the developmental progression of the day 4 pre-implantation embryos produced in vitro . This developmental delay could not be attributed to a loss of sperm DNA integrity, DNA damage, or elevated levels of intracellular reactive oxygen species. When considered together, the results presented here raise the intriguing prospect that spermatozoa exposed to a short-term PFAS exposure period potentially harbor an alternate stress signal that is delivered to the embryo upon fertilization.
Lay summary
PFAS are synthetic chemicals widely used in non-stick cookware, food packaging, and firefighting foam. Such extensive use has led to concerning levels of environmental contamination and reports of associations with a spectrum of negative health outcomes, including testicular cancer and reduced semen quality. To investigate the effects of PFAS on male reproduction, we incubated mouse sperm in a cocktail of nine PFAS at environmentally relevant concentrations before checking for a range of functional outcomes. This treatment strategy was not toxic to the sperm; it did not kill them or reduce their motility, nor did it affect their fertilization capacity. However, we did observe developmental delays among pre-implantation embryos created using PFAS-treated sperm. Such findings raise the intriguing prospect that PFAS-exposed sperm harbor a form of stress signal that they deliver to the embryo upon fertilization.
Purpose of review
This review aims to compare evidence on four criteria (embryo implantation, obstetric outcomes, patient convenience, and IVF-unit efficiency) by analyzing published research on different endometrial preparation methods for frozen embryo transfer (FET).
Recent findings
While the artificial-FET cycle provides advantages in scheduling and implantation, it falls short in ensuring optimal obstetric outcomes. In contrast, natural-FET ensures embryo implantation conditions if ovulation is correctly identified. Supplementing with exogenous progesterone shields against low corpus luteum progesterone secretion, crucial for positive obstetric outcomes. In mNC-FET, ovulation is hCG-triggered, closely resembling natural cycles and reducing monitoring visits for enhanced patient convenience.
Letrozole is a recommended option for anovulatory patients, preserving endometrial thickness. It is cost-effective, less likely to induce multifollicular development than gonadotropins, and better tolerated.
In a novel approach, the natural-proliferative-phase-FET initiates progesterone in an unmediated ovulatory cycle at 7 mm endometrial thickness, combining the benefits of a natural proliferative endometrium with the convenience of scheduled artificial cycles.
Summary
The artificial cycle offers scheduling advantages, but may compromise obstetric outcomes. Natural FET relies on accurate ovulation timing for successful implantation. mNC-FET simplifies the process using hCG induction, minimizing clinic visits for improved convenience. Letrozole is highlighted as a cost-effective and well tolerated option in anovulatory patients. A recent innovative approach combines elements of natural and artificial cycles, showing promise for FET procedures.
Genes for chorionic gonadotrophin (CG) are transcribed by the 16-cell embryo stage in humans, but there is no clear evidence of CG secretion as a bioactive dimer before attachment and trophoblast outgrowth stages of implantation. The studies summarized question the timing of CG expression and secretion, the possible roles of CG for intraembryonic differentiation and at the implantation site, and the recognition of this primate embryo-derived signal in support of the corpus luteum. The data suggest that the implantation window in primates may be broader than in non-primate species, where a closer synchrony between embryonic, tubal and uterine events appears to be necessary for embryonic survival. Some preliminary data concerning an association between peripheral thrombocytopenia, ovarian inhibin secretion and peri-implantation stages of embryo development indicate that an unknown embryonic signal may be secreted before bioactive CG can be detected.
Embryo implantation involves a series of complex interactions between the developing embryo and the maternal endometrium. Results of studies with animal models suggest that the uterus must undergo a series of morphological and biochemical changes, mediated primarily by oestrogen and progesterone, before it becomes receptive for successful implantation. At present there is little understanding of the endometrial changes required to achieve endometrial receptivity for implantation in the human. It appears that control of receptivity is not as stringent in the human as in some other species, with IVF data suggesting that the duration of receptivity is at least 4 days, and that successful implantation can occur under a relatively wide range of morphological and ultrastructural conditions. Research on the later stages of implantation, including embryo positioning within the uterus, attachment and invasion, has been almost non-existent in the human. Further studies are critical for a better understanding of this complex process, although human studies will always be limited by ethical constraints.
Of 48 spare human pre-embryos achieving the expanded blastocyst stage, 22 (45.6%) secreted significant amounts of human chorionic gonadotrophin (HCG) (>5 IU/l/day). Of these, nine remained intrazonal, seven partially hatched and six fully hatched. Embryonic production of HCG in vitro appeared to be time-dependent, starting after a certain minimum time (∼160 h post-insemination) and rising exponentially, with maximal HCG production around day 10. Hatching was not a prerequisite for HCG secretion, since similar amounts were produced by intrazonal blastocysts. Blastocysts derived from abnormally fertilized oocytes also began secreting HCG exponentially but secretion was delayed and the upper limit of maximum HCG secretion rate was comparatively low. The actual amount of HCG is thought to reflect the number of viable trophectoderm cells producing the hormone. HCG doubling times for blastocysts in vitro were rapid when compared to implanting blastocysts of a similar age in vivo, with 19/22 (86.4%) blastocysts having a doubling time of < 10 h. Provided a pre-embryo can secrete HCG and maintain an adequate doubling time, sufficient HCG should be produced for initial stages of embryonic recognition in vivo. Since intrazonal blastocysts are capable of fulfilling both of these criteria, the limiting factor in realizing their full potential may be escaping from the zona pellucida.
Pregnancy rates vary considerably with the type of ovarian stimulation used for in vitro fertilization and embryo transfer (IVF-ET). The window of implantation may represent one of the rate-limiting steps in IVF success. We therefore investigated estimated implantation times of 10 consecutive IVF singleton pregnancies, achieved using pituitary suppression with gonadotropin-releasing hormone agonist (GnRH-a) before and during ovarian stimulation with human menopausal gonadotropins (hMG), and compared those with 9 consecutive IVF pregnancies achieved by hMG stimulation only. Estimated implantation times were calculated by regression analysis of serial human chorionic gonadotropin (hCG) measurements between days 7 and 16 after ET. The GnRH-a/hMG pregnancies implanted between days 7 and 11, whereas hMG pregnancies implanted between days 7 and 9 after ET. The hCG regression curve for the GnRH-a/hMG pregnancies revealed a delay of 1.5 days in estimated implantation time compared with the hMG only group. There were no significant differences in pretransfer in vitro embryos development between the two groups. Thus, the delay in hCG rise probably reflects a delay in embryo implantation. We therefore conclude that a GnRH-a/hMG stimulation protocol appears to widen the implantation window in comparison with a hMG only protocol. This observation may at least in part explain the improved IVF pregnancy success with GnRH-a/hMG stimulation protocols.
We intensively studied 30 women attempting pregnancy in order to lay groundwork for larger studies of early pregnancy loss. These women collected first morning urine specimens for up to 6 months after discontinuing use of birth control. Urine specimens were successfully collected for 98% of the woman-days in the study. Three assays for human chorionic gonadotropin (hCG) were performed on each urine specimen. An immunoradiometric assay (IRMA) specific to the carboxy terminal peptide of the hCG β -chain proved to be more sensitive and more specific than two radioimmunoassays (RIAs). Using the IRMA, we found four cases in which hCG rose and fell over successive days, consistent with early pregnancy loss. For three of these four cases, the level of hCG was too low to be detectable with the RIAs. Among the control group of five women with tubal ligations, there was no detectable hCG above threshold with the IRMA. Thus, the enhanced sensitivity and specificity of the IRMA allows very early pregnancy losses to be identified that would otherwise be undetectable. Furthermore, its effectiveness with small quantities of first morning urine makes the IRMA a useful tool for epidemiologic studies.
We have developed a method of estimating day of ovulation using urinary ovarian hormone data. The method identifies a day of luteal transition that occurs at the shift from production of follicular oestrogen to luteal progesterone. The algorithm for identifying this shift was evaluated and judged better than specified alternatives in that it resulted in (1) a high concordance between the day of luteal transition and peaks in urinary luteinizing hormone (LH) for cycles with well-defined peaks, (2) a low variance in the length of the luteal phase of the menstrual cycle, which presumably reflects a low measurement error in estimating day of ovulation, and (3) a high proportion of cycles for which an approximate day of ovulation could be determined. To validate the new algorithm, it was applied to an independent data set. The algorithm identified a day of luteal transition in 88 percent of these cycles, and the identified day occurred within two days of the urinary LH peak for all of the cycles with clear LH peaks. Determination of the day of luteal transition to estimate ovulation requires only first-morning urine specimens, requires no correction for day-to-day variations in urine concentration, and can be applied to a mid-ycle window of data.
Human in vitro fertilization is characterized by a low of ficiency of implantation. Possible mechanisms for pregnancy loss are discussed. Embryo viability or quality, abnormal implantation, and delayed or absent corpus luteum rescue may all play a role in pregnancy wastage. Defining the possible mechanism for these losses may allow hormonal treatment to correct specific abnormalities.
4th Ed Bibliogr. na konci kapitol
Direct radioimmunoassay are described for the measurement of each of three specific estrogen glucosiduronates: estrone glucosiduronate, 17 beta-estradiol-17-glucosiduronate and estriol-16 alpha-glucosiduronate in urine. Each assay utilizes a specific antiserum prepared by complexing the carboxylic acid group of the appropriate glucosiduronate to the epsilon-amino group of lysine in bovine serum albumin or bovine thyroglobulin. The antisera showed little or no cross reactivity toward other estrogens that might be present in significant amounts in urine. These antisera were used for the direct assay of the conjugates in urine from normal men and nonpregnant women without prior extraction or chromatography. The values were similar to those obtained after extraction, chromatographic purification on DEAE-Sephadex and subsequent immunoassay; The following mean values +/- SE (microgram/g creatinine) were obtained: estrone glucosiduronate, male 10.1 +/- 0.6, follicular phase female 17.3+/- 1.6, luteal phase female 31.8 +/- 2.5; 17 beta-estradiol-17-glucosiduronate, male 1.7 +/- 0.3, follicular phase female 2.4 +/- 0.1, luteal phase female 4.2 +/- 0.4; estriol-16 alpha-glucosiduronate, male 1.8 +/- 0.2, follicular phase female 4.7 +/- 0.9, luteal phase female 10.0 +/- 1.6.
An antibody was prepared against pregnanediol-3α-glucuronide-BSA. The hapten (5β-pregnane-20α-ol-3α-yl-glucuronide) used for the preparation of the immunogen and as ‘cold’ standard for RIA was synthesized by an unambiguous chemical synthesis. The corresponding [6,7-3H]-labelled conjugate was prepared and the cross-reactions of the antiserum against other glucuronides and free steroids were examined. Application of RIA to menstrual cycle urines and pregnancy urine is discussed. The results of our own studies carried out throughout the menstrual cycle from seven women showed the mean and range for the follicular phase were 3.8 ± 0.67 (3.0 – 5.4) μmol/24 h and for the luteal phase 17.7 ± 6.9 (6.9 – 29.0) μmol/24h.
The WHO Expert Committee on Biological Standardization has established CR119 HCG, CR119 HCGα, and CR119 HCGβ3 as reference preparations for the immunoassay of human chorionic gonadotrophin (HCG) and its subunits. CR119 HCG has interstitial cell stimulating activities of 13 450 IU/mg (bioassay, Second International Standard for HCG) and proportional thyroid stimulating and follicle stimulating activities when tested in vivo. In the subunit preparations, the potencies of these activities are uniformly less than 0.02 relative to the undissociated hormone, and approximately 75% of the activity of each is recovered after recombination. The chemical, physical, and antigenic properties of each preparation are consistent with those reported for preparations of equivalent purity.
Human CG (hCG) was administered to three groups of four normally cycling women in the early luteal phase (LH +4 to +5, group I), the midluteal phase (LH +8 to +9, group II), and the late luteal phase (LH +11 to +12, group III). Two hundred and fifty IU hCG were given im followed in half of the subjects by 750 IU hCG 24 h later. Serial blood samples were then taken at 15- or 30-min intervals following either the first or second hCG injection and continued for 12 or 24 h. The samples were stored frozen at -20 C until assayed for LH, progesterone, estradiol, and hCG concentrations. Treatment with 250 IU hCG at each stage of the luteal phase did not result in any marked change in hormone concentrations. Further hCG administration (750 IU 24 h later) in both the early and the midluteal phases elicited a clear increase in progesterone concentrations. Further hCG treatment in the late luteal phase did not evoke any rise in progesterone levels. Further hCG administration in the midluteal phase resulted in a sharp decline in LH concentrations, brought about mainly by a decrease in LH pulse frequency, this response was not apparent at any other stage of the luteal phase. Despite the lack of any pulsatile steroidogenic stimulus at this time, progesterone was clearly secreted in a pulsatile manner. The decline in LH levels following hCG administration in the midluteal phase resembled that seen in spontaneous conception cycles following implantation. The restriction of this response to the time of normal implantation may suggest a role for the pituitary in the establishment of the "implantation window." The importance of this pituitary response and the mechanisms involved are currently unknown. Its absence in the early luteal phase would suggest that it cannot be directly attributed to either progesterone or hCG. It is possible that some other luteal factor may be responsible for the midluteal decline in LH concentrations.
Excerpt
Sheffield Fertility Centre, 26 Glen Road, Sheffield, S7 1RA, UK and University Department of Obstetrics and Gynaecology, Jessop Hospital for Women, Leavygreave Road, Sheffield, S3 7RE, UK
Keywords: implantation; in-vitro fertilization; pregnancy; pregnancy loss; human chorionic gonadotrophin; human
Introduction The endocrine characteristics of normal human pregnancy have been difficult to establish, chiefly because spontaneous pregnancies occur unpredictably. More reliable sources of early pregnancy data are conceptions following various assisted reproductive technologies although, unfortunately, many of these may not be useful for determining normal physiology, firstly, because there is multiple follicle development resulting from the use of exogenous gonadotrophins and, secondly, because human chorionic gonadotrophin (hCG) given to induce luteinization masks hCG from the implanting embryo. Furthermore, the practice, at least for in-vitro fertilization (IVF), of replacing up to 3 embryos renders assessment of the number of implantation sites uncertain.
In-vitro fertilization in the natural or spontaneous cycle may provide
Loss of a conceptus early in development can be detected by very sensitive assays specific for hCG. We examined 20 menstrual cycles ending in early loss of a conceptus in order to identify hormonal correlates of loss. Each loss cycle was compared to a successful conception cycle in the same woman, using daily concentration of urinary estrone-3-glucuronide and pregnanediol-3-glucuronide (PdG). The estrone-3-glucuronide and PdG profiles in cycles of early pregnancy loss were very similar to those in successful conception cycles until late in the luteal phase. Early pregnancy loss was not related to a midluteal deficiency in PdG. hCG tended to be detected later in cycles of early pregnancy loss than in successful conception cycles, presumably indicating later implantation. Ten of the early pregnancy losses implanted after luteal-day-10; only one of the successful pregnancies implanted that late. The corpus luteum responded to the conception in only 2 of the 10 loss cycles with late implantation. In contrast, the corpus luteum responded in 8 of 10 loss cycles with normally timed implantation. The similarity of preimplantation hormonal profiles in cycles of early pregnancy loss and in cycles with successful conceptions suggests that most early losses in reproductively normal women do not result directly from deficiencies in ovarian steroid production.
Human in vitro fertilization is characterized by a low efficiency of implantation. Possible mechanisms for pregnancy loss are discussed. Embryo viability or quality, abnormal implantation, and delayed or absent corpus luteum rescue may all play a role in pregnancy wastage. Defining the possible mechanism for these losses may allow hormonal treatment to correct specific abnormalities.
We looked at risk of early pregnancy loss among 171 women who conceived while participating in study. Twenty-five percent of biochemically detected pregnancies ended within six weeks of the last menstrual period; all but two of these losses were clinically unrecognized. While our sample is small, it is the first to allow description of possible associations between risk of early pregnancy loss and maternal characteristics or exposures. We looked at risk in relation to a woman's age, pregnancy history, weight, education, prenatal DES exposure, cigarette smoking, use of caffeinated and alcoholic beverages, marijuana, cigarette smoking by baby's father, and other variables. None of these factors was definitely associated with early pregnancy loss. Still, the possibility of real effects cannot be excluded and deserves further study.
Pregnancy rates vary considerably with the type of ovarian stimulation used for in vitro fertilization and embryo transfer (IVF-ET). The window of implantation may represent one of the rate-limiting steps in IVF success. We therefore investigated estimated implantation times of 10 consecutive IVF singleton pregnancies, achieved using pituitary suppression with gonadotropin-releasing hormone agonist (GnRH-a) before and during ovarian stimulation with human menopausal gonadotropins (hMG), and compared those with 9 consecutive IVF pregnancies achieved by hMG stimulation only. Estimated implantation times were calculated by regression analysis of serial human chorionic gonadotropin (hCG) measurements between days 7 and 16 after ET. The GnRH-a/hMG pregnancies implanted between days 7 and 11, whereas hMG pregnancies implanted between days 7 and 9 after ET. The hCG regression curve for the GnRH-a/hMG pregnancies revealed a delay of 1.5 days in estimated implantation time compared with the hMG only group. There were no significant differences in pretransfer in vitro embryos development between the two groups. Thus, the delay in hCG rise probably reflects a delay in embryo implantation. We therefore conclude that a GnRH-a/hMG stimulation protocol appears to widen the implantation window in comparison with a hMG only protocol. This observation may at least in part explain the improved IVF pregnancy success with GnRH-a/hMG stimulation protocols.
Paired blood and urine samples were obtained from patients between the sixth and 14th weeks of normal pregnancy. The levels of intact human chorionic gonadotropin (hCG), and of the free alpha and beta subunits, were measured by specific immunoassays. There was a close association between blood and urine levels of intact hCG and of the alpha subunit of hCG, but no relation between the levels of beta subunit in these sites. These findings suggest that the use of "beta subunit" assays may give discrepant results according to the fluid examined. By contrast, measurement of intact hCG appears to give similar results in blood and urine.
Human chorionic gonadotrophin beta (HCG-beta) is a trophoblast marker. Its expression is normally limited to syncytiotrophoblast cells of chorionic villi, although it is known to be secreted from the human embryo as early as 7 days post-fertilization. To examine the onset of embryonic transcriptional activity of the gene encoding this polypeptide we have performed in-situ hybridization to cellular RNAs of human tripronucleate preimplantation embryos. We see expression of HCG-beta RNA at the 6-8-cell stage, before morphological differentiation between trophectoderm and inner cell mass is apparent. We believe that this RNA is the product of de novo transcription from the embryonic genome, since transcripts are only observed in embryos of at least 2 days post-fertilization in age.
Following in vitro fertilization, the criteria commonly used to select human embryos for transfer are the cleavage rate and gross morphology, the contention being that those embryos which divide more rapidly and have regular, spherical blastomeres are more likely to lead to a pregnancy. In order to assess the validity of this assumption, the development in vitro of spare embryos was investigated. Eggs and embryos were cultured in Earle's balanced salt solution containing 10% heat-inactivated patient's serum, and insemination was performed at 40 hr post human chorionic gonadotropin (hCG). At 82-90 hr post hCG, up to four embryos were transferred. Any spare embryos were cultured in the same medium for up to 6 days and scored daily for cell number and morphology using a "quality" scale of 4-1 according to degree of fragmentation and shape of the blastomeres. Of 317 fertilized eggs, 55 (17%) developed to the fully expanded blastocyst stage. The remaining embryos ceased development at the one-cell (6; 2%), two-cell (49; 15%), four-cell (110; 35%), eight-cell (61; 19%), and cavitating morula (36; 11%) stages. The relationship between developmental arrest and gross morphology is discussed.
The receptivity for blastocyst implantation is controlled by progesterone and in some species by the synergistic action of progesterone and estrogen. The duration of the receptive phase, the so-called "window," is short in rodents (less than 24 hours) and may be three days in the primate. Once the uterus becomes receptive, it automatically becomes refractory at the end of the receptive phase. The uterus in the refractory phase can be toxic to the blastocyst in small laboratory animals. The endometrium of the receptive uterus may be characterized by the following parameters: (1) Formation of bulbous protrusions on the apical surface of the luminal epithelium; (2) Secretion of the stage-specific glycoproteins by the luminal epithelium; (3) Readiness of stromal cells to decidualize when appropriate stimulation is applied; and (4) Reorganization and changes of stromal extracellular matrix components so that stromal cells are conditioned for decidualization, and after decidualization the appearance of basement membrane components in the matrix.
We studied the risk of early loss of pregnancy by collecting daily urine specimens from 221 healthy women who were attempting to conceive. Urinary concentrations of human chorionic gonadotropin (hCG) were measured for a total of 707 menstrual cycles with use of an immunoradiometric assay that is able to detect hCG levels as low as 0.01 ng per milliliter, with virtually 100 percent specificity for hCG in the presence of luteinizing hormone. Our criterion for early pregnancy--an hCG level above 0.025 ng per milliliter on three consecutive days--was determined after we compared the hCG levels in the study group with the levels in a comparable group of 28 women who had undergone sterilization by tubal ligation. We identified 198 pregnancies by an increase in the hCG level near the expected time of implantation. Of these, 22 percent ended before pregnancy was detected clinically. Most of these early pregnancy losses would not have been detectable by the less sensitive assays for hCG used in earlier studies. The total rate of pregnancy loss after implantation, including clinically recognized spontaneous abortions, was 31 percent. Most of the 40 women with unrecognized early pregnancy losses had normal fertility, since 95 percent of them subsequently became clinically pregnant within two years.
We intensively studied 30 women attempting pregnancy in order to lay groundwork for larger studies of early pregnancy loss. These women collected first morning urine specimens for up to 6 months after discontinuing use of birth control. Urine specimens were successfully collected for 98% of the woman-days in the study. Three assays for human chorionic gonadotropin (hCG) were performed on each urine specimen. An immunoradiometric assay (IRMA) specific to the carboxyterminal peptide of the hCG beta-chain proved to be more sensitive and more specific than two radioimmunoassays (RIAs). Using the IRMA, we found four cases in which hCG rose and fell over successive days, consistent with early pregnancy loss. For three of these four cases, the level of hCG was too low to be detectable with the RIAs. Among the control group of five women with tubal ligations, there was no detectable hCG above threshold with the IRMA. Thus, the enhanced sensitivity and specificity of the IRMA allows very early pregnancy losses to be identified that would otherwise be undetectable. Furthermore, its effectiveness with small quantities of first morning urine makes the IRMA a useful tool for epidemiologic studies.
A highly sensitive and specific two-site immunoradiometric assay (IRMA) for hCG has been developed and applied to the detection of the hormone in the urine of normal nonpregnant and pregnant individuals. The IRMA uses a solid phase coupled monoclonal antibody to the hCG beta-subunit for extraction of hormone from urine. The hCG extracted is then directly quantified by the binding of an affinity purified and radiolabeled rabbit antibody that reacts with the unique COOH-terminal peptide region of the hCG beta-subunit. The assay is capable of reliably and accurately measuring as little as 0.01 ng hCG/ml urine without interference from hLH. Assays of urine from normal men and nonpregnant women of reproductive age indicated that most individuals did not have detectable levels of hCG immunoreactivity, although a minority had minute amounts, with a mean value of approximately 0.01 ng hCG/mg creatinine. In contrast, all normal menopausal women studied had easily detectable levels of hCG immunoreactivity in their urine, with a mean value of 0.123 ng hCG/mg creatinine. A study of the excretion of hCG from three men injected with hormone for treatment of infertility indicated that after the first 24 h, hCG was cleared with a single exponential rate and was detectable to a level of 0.01 ng/ml. Application of the IRMA to measurements of hCG in the urine of two artificially inseminated patients indicated that the method was capable of detecting pregnancy as early as 9 days postovulation. The extreme sensitivity and specificity of the IRMA for urinary hCG in conjunction with the simplicity of assay performance and specimen collection should provide a substantial advantage over currently available methods for detection of early pregnancy and tumor monitoring.
The preimplantation effects of progesterone antagonists on the cell biology of the endometrium, corpus luteum function and interactions between these two organs have been studied. The antagon ists lilopristone (ZK 98.734) and onapristone (ZK 98.299) were initially given per os to rabbits early or late in pseudopregnancy in combination with human chorionic gonadotrophin (HCG). These protocols were then modified to include hysterectomy or luteotrophic support with 17β-oestradiol. Given alone, the antagonists gave rise to endometrial regression (inhibition of epithelial proliferation and differentiation, increase of apoptosis). The simultaneous addition of oestradiol did not alter these findings. A rapid luteolysis occurred when the antagonists were given in late pseudopregnancy, but not if combined with oestradiol or hysterectomy. The endometrium was capable of renewal and of sustaining implantation if the corpora lutea survived or oestradiol was administered, and transferred blastocysts displayed normal implantation and normal embryonic development. These events did not occur when the antagonists were given during late pseudopregnancy without any steroid supplement.
Progesterone antagonists can evidently exert a direct inhibitory effect on the endometrium, possibly with a later indirect luteolytic effect via endometrial mediators. Simultaneous addition of a proper luteotrophic signal results in corpora lutea which are refractory to lysis, so revealing a potential functional dissociation between endometrium and corpus luteum. The endometrium has the capacity to differentiate normally after an interrupted transformation and becomes receptive and sustains normal pregnancy, due to an expanded lifespan of the corpora lutea and a transposition of the implantation window. Uterine secretions from patients undergoing in-vitro fertilization, collected at the onset of the luteal phase, were evaluated by SDS-PAGE densitometry. The protein profiles gave indications of an adequate luteal phase pattern and of a receptive preimplantation phase. These results open the prospect of manipulating the human implantation window.
To examine whether opening of the zona pellucida (i.e., assisted hatching) accelerates implantation.
In a controlled, randomized trial, patients were assigned to control and assisted hatching groups.
All patients studied were of the Center for Reproductive Medicine at Cornell University Medical College.
All patients underwent stimulation with gonadotropins after luteal phase GnRH down regulation. Assisted hatching with zona drilling using acidic Tyrode's solution was performed on the assigned embryos.
Luteal E2, P, and hCG on days +5, +6, +7, +8, +9, +11, +13, and +15 were measured. The implantation time, peak midluteal E2 and intervals between these two values were studied.
Implantation occurred significantly earlier in the assisted hatching group. The interval between implantation and peak midluteal E2 was also significantly shorter in the assisted hatching group than in the controls. However, there was no significant difference in the day of the peak midluteal E2 between the assisted hatching and control groups.
Assisted hatching may enhance embryo implantation not only by mechanically facilitating the hatching process but also by allowing earlier embryo-endometrium contact. Such early contact may enhance embryonic development potential and may optimize synchronization between embryo and endometrium, resulting in improved implantation efficiency.
Of 48 spare human pre-embryos achieving the expanded blastocyst stage, 22 (45.6%) secreted significant amounts of human chorionic gonadotrophin (HCG) (> 5 IU/l/day). Of these, nine remained intrazonal, seven partially hatched and six fully hatched. Embryonic production of HCG in vitro appeared to be time-dependent, starting after a certain minimum time (approximately 160 h post-insemination) and rising exponentially, with maximal HCG production around day 10. Hatching was not a prerequisite for HCG secretion, since similar amounts were produced by intrazonal blastocysts. Blastocysts derived from abnormally fertilized oocytes also began secreting HCG exponentially but secretion was delayed and the upper limit of maximum HCG secretion rate was comparatively low. The actual amount of HCG is thought to reflect the number of viable trophectoderm cells producing the hormone. HCG doubling times for blastocysts in vitro were rapid when compared to implanting blastocysts of a similar age in vivo, with 19/22 (86.4%) blastocysts having a doubling time of < 10 h. Provided a pre-embryo can secrete HCG and maintain an adequate doubling time, sufficient HCG should be produced for initial stages of embryonic recognition in vivo. Since intrazonal blastocysts are capable of fulfilling both of these criteria, the limiting factor in realizing their full potential may be escaping from the zona pellucida.
Objective:
We determined the ovarian response to human chorionic gonadotrophin (hCG) in terms of relaxin and progesterone secretion during the peri-implantation period of normal and failing pregnancies. We wished to test the hypotheses that relaxin production in failing pregnancies is different from that in normal pregnancies, that relaxin is a reliable, quantitative indicator of the biological activity of endogenous hCG, and that relaxin is a useful predictor of peri-implantation spontaneous abortions.
Design:
Daily blood samples were collected in a prospective longitudinal study from insemination patients.
Patients:
Women undergoing artificial insemination in natural cycles with non-frozen donor semen at a University clinic.
Measurements:
Serum LH, hCG, relaxin and progesterone were measured and the relationship between hCG and the ovarian hormones was evaluated in the peri-implantation period of normal pregnancies and spontaneous abortions.
Results:
Nine of 23 conceptive cycles resulted in a spontaneous abortion between 16 and 70 days after the LH peak. In all normal and failing pregnancies there was a close qualitative relationship between hCG secretion and relaxin production. Six of nine failing pregnancies were associated with abnormally low hCG secretion. Six of the spontaneous abortions were associated with rates of relaxin secretion which were higher than the mean of 14 normal pregnancies. No such alterations in progesterone concentrations were observed. In cases where hCG was extremely low, the quantitative relationship between hCG and relaxin was different from that in cases of normal hCG concentrations.
Conclusions:
There is a close temporal relationship between the secretion of trophoblastic hCG and ovarian secretion of relaxin in the peri-implantation period of normal and failing pregnancies. In failing pregnancies there is substantial variability in the quantitative relationship between relaxin and hCG, indicating that relaxin is not a reliable quantitative indicator of hCG bioactivity. Contrary to previous reports, relaxin concentrations in failing pregnancies tended to be higher than or equal to concentrations in normal pregnancies until the loss was imminent. Because of this relaxin is not a useful predictor of peri-implantation spontaneous abortions.
Longitudinal epidemiologic studies of menstrual and reproductive function are more informative if one can identify day of ovulation. We previously developed a method for estimating day of ovulation that is feasible for epidemiologic studies. The method relies on the relative concentrations of estrogen and progesterone metabolites in daily first-morning urine specimens and does not require creatinine adjustment. This paper describes results of applying this method to a large study with 724 menstrual cycles from 217 women. The method estimated a credible day of ovulation in 88% of cycles. Missing data accounted for most of the failures. When we excluded anovulatory cycles (1%) and cycles with missing data, the method estimated a day of ovulation in 97% of cycles. Variance in luteal phase length was small for our sample, suggesting that this method of identifying a day of ovulation introduces no more measurement error than when day of ovulation is determined by plasma luteinizing hormone (LH), the standard clinical method.
To gain insight into the physiology of human endometrial development after artificial preparation with estrogen (E) and P, before oocyte donation.
Review and analysis of relevant studies published in the last decade, identified through the literature and Medline searches.
Oocyte donation represents a unique in vivo experimental model in the human that permits the study of endometrial development under controlled variable conditions. Early studies have shown that adequate endometrial preparation can be achieved by sequential E and P only. The successful implementation of the simplified approach to oocyte donation demonstrated that satisfactory endometrial receptivity is not dependent on incremental administration of E and P and similarly can be achieved by fixed dosages of these steroids. Moreover, numerous clinical oocyte donation studies have shown that both physiologic and supraphysiologic levels of E and P have resulted in good endometrial development and pregnancy rates, underlining the relative insensitivity of the endometrium to extreme hormonal conditions. In addition, it has been clarified that the endometrium is tolerant of some manipulations during the follicular phase. Contrary to morphological studies that demonstrated preservation of endometrial preparation after luteal E depletion, preliminary evidence suggests that the functional capacity of the endometrium could be affected adversely.
In contrast to early oocyte donation studies, which indicated a correlation between morphologic integrity and functional capacity of the endometrium, some evidence presented in this review demonstrates that adequate endometrial morphology does not always imply normal endometrial receptivity.
Integrins belong to a family of cell adhesion molecules that are present on virtually all cells. The temporal and spatial expression of these important proteins on the human endometrium suggests that certain integrins may participate in the cascade of molecular events leading to successful implantation.
Using immunohistochemistry, we studied the expression of 12 different integrins in up to 600 samples of human endometrium throughout the menstrual cycle. Intensity and distribution of staining was determined using the semiquantitative HSCORE, with specific focus on the differences between glandular and luminal expression.
We noted that the glandular and luminal epithelium undergo independent alterations in integrin expression throughout the menstrual cycle. Specifically, glandular epithelium express certain integrins only during the window of implantation, while luminal epithelium down-regulate certain integrins during this time. The expression of one integrin (the alpha v beta 3 vitronectin receptor) on both luminal and glandular epithelium coincides with the time of embryo attachment; aberrant expression of this integrin is associated with infertility.
It appears that the endometrium is a unique tissue with regard to the number of integrins that undergo temporal and spatial changes during the menstrual cycle. These data may offer new directions for the development of a novel contraceptive approach targeted to the endometrium as well as a better understanding of occult causes of infertility in women.
As implantation approaches the different endometrial components demonstrate certain anatomical and molecular changes. Molecules with an effect on uterine receptivity for blastocyst implantation include integrins, leukaemia inhibitory factor (LIF), interleukin-1 (IL-1) and colony stimulating factor-1 (CSF-1). Although over the past 5 years our understanding of the implantation process has improved dramatically, there are still many unanswered questions. Undisputed morphological, biochemical and molecular markers of uterine receptivity that permit quantification of the human implantation window are still unknown. The factors which regulate the expression of integrins, LIF, CSF-1 and IL-1, the mode of action of these molecules and their role in human implantation remain unclear. Only when these questions are answered shall we be able to apply the molecular aspects of implantation to clinical practice.
From a study of 34 early human ova (24 normal and 10 abnormal) recovered from a series of 107 patients known to be fertile whose conditions for conception were optimal it appears that the maximum fertility rate at implantation is 58%; the maximum normal fertility rate after the twelfth day of ovular development is 42%; the probable maximum fertility rate during the preimplantation stages is from 80 to 90%; the greatest ovular loss is in the preimplantation stage; the next greatest loss is during the week after implantation; the ovular loss after the first missed period may be as great as 28.6%, either with or without clinical signs and is therefore comparable to the clinical abortion rate; these defective human fertilized ova rise because of intrinsic defects rather than from defects of the local or endocrine environment, and, finally, the fertility rates and fate of fertilzed ova are roughly comparable in man and other mammals.
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