Comparing thaw survival, implantation and live birth rates from cryopreserved zygotes, embryos and blastocysts.
ABSTRACT Most in vitro fertilization (IVF) programs employ embryo cryopreservation to enhance pregnancies from a single ovarian stimulation. More embryos are created, some of which are not transferred to the uterus immediately, generating a need for improved cryopreservation protocols. One protocol may involve growing embryos to a further stage of development, allowing only embryos with proven developmental capabilities to be cryopreserved. Here we examined thaw survival, implantation and live birth rates of embryos cryopreserved at different stages.
We examined thaw survival, implantation and live birth rates of embryos cryopreserved at the zygote, day 3 (D3) embryos or blastocyst stage.
This is a retrospective study from a single academic IVF program.
A retrospective study of all patients who had frozen embryos transferred to their uteri from year 2002 to 2008 at a single academic IVF program was conducted.
Analysis of variance followed by Fisher's Exact Test was performed to compare the survival after thaw, implantation and live birth rates between the three groups.
One thousand nine hundred and ninety-one zygotes, 2880 D3 embryos and 503 blastocysts were frozen using a slow freeze technique, thawed and transferred. Significantly more D3 embryos and blastocysts survived the thawing process compared to zygotes and significantly higher implantation rate per number of thawed blastocysts was achieved than that for zygotes. Live birth rates were similar between the three groups.
Growing embryos to blastocyst stage prior to cryopreservation is associated with fewer frozen embryos but does not appear compromise patients' chance of achieving pregnancy.
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ABSTRACT: The introduction and widespread application of assisted reproduction techniques have raised major concern about the outcome of resulting pregnancies, as well as about the offspring's health. It seems that pregnancies achieved after standard in-vitro fertilization (IVF) bear an increased risk for prematurity and low birth weight. On the other hand, pregnancy outcome of singletons achieved after intracytoplasmic sperm injection (ICSI) and after the transfer of frozen-thawed embryos is similar to that of spontaneously conceived singletons, and pregnancy complications are related only to gestation multiplicity. The incidence of congenital and chromosomal anomalies after standard IVF seems to be similar to that expected in the general population. The prevalence of congenital malformations does not seem to be higher after ICSI. On the other hand, there is a slightly increased risk for transmission of chromosomal aberrations of paternal origin and a higher risk of de novo, mainly sex-chromosomal aberrations. Postnatal growth and development of children born after standard IVF and cryopreservation seem to be within the normal ranges. Growth of ICSI children is also normal while their mental development needs further investigation. Family functioning in assisted reproduction families is better.Human Reproduction 10/1999; 14 Suppl 1:231-42. · 4.67 Impact Factor
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ABSTRACT: To evaluate the impact of cryopreservation storage duration on embryo survival, implantation competence, and pregnancy outcome. Retrospective study. Academic tertiary-referral infertility center. In vitro fertilization patients and recipients of oocyte donation cycles who had cryopreserved embryos and underwent at least one thaw cycle from 1986 to 2007. None. Postthaw survival proportion and implantation, clinical pregnancy, miscarriage, and live birth rates. Length of storage time did not have a significant effect on postthaw survival for IVF or oocyte donation cycles, or for embryos frozen at the pronuclear or cleavage stages. There was no significant impact of the duration of storage on clinical pregnancy, miscarriage, implantation, or live birth rate, whether from IVF or oocyte donation cycles. Logistic regression analysis demonstrated that the length of storage time or developmental stage at freezing were not predictive of embryo survival or pregnancy outcome. Only oocyte age, survival proportion, and number of transferred embryos were positive predictors of pregnancy outcome. Cryostorage duration did not adversely affect postthaw survival or pregnancy outcome in IVF or oocyte donation patients.Fertility and sterility 12/2008; 93(1):109-15. · 3.97 Impact Factor
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ABSTRACT: To summarize the available evidence from randomized controlled trials comparing vitrification versus slow freezing for cryopreservation of human embryos. Vitrification, as compared with slow freezing, appears to be better in terms of postthawing survival rates both for cleavage-stage embryos [odds ratio (OR): 6.35, 95% confidence interval (CI): 1.14-35.26, random effects model] and for blastocysts (OR: 4.09, 95% CI: 2.45-6.84, random effects model). Furthermore, postthawing blastocyst development of embryos cryopreserved in the cleavage stage is significantly higher with vitrification as compared with slow freezing (OR: 1.56, 95% CI: 1.07-2.27, fixed effects model). No significant difference in clinical pregnancy rates per transfer could be detected between the two cryopreservation methods (OR: 1.66, 95% CI: 0.98-2.79). Currently, vitrification does not appear to be associated with an increased probability of pregnancy. However, a significant advantage of vitrification over slow freezing in terms of postthawing survival rates is present for embryos cryopreserved both at the cleavage and at the blastocyst stages. The above conclusions are based on limited data, and thus further properly designed randomized controlled trials are needed.Current opinion in obstetrics & gynecology 04/2009; 21(3):270-4. · 2.49 Impact Factor