Article

Does the saltatory pattern on cardiotocograph (CTG) trace really exist? The ZigZag pattern as an alternative definition and its correlation with perinatal outcomes

The Journal of Maternal-Fetal & Neonatal Medicine

November 2019
34(5):1-9

DOI:10.1080/14767058.2019.1686475

Authors:

Kugajeevan Vigneswaran

King's College Hospital NHS Foundation Trust

Daniel Cuadras

IQVIA

Edwin Chandraharan

Global Academy of Medical Education & Training

Background: The saltatory pattern (SP) has been defined by guidelines as a uniformly increased bandwidth of >25 beats per min lasting for 30 min. However, previous research suggest that it is very unusual to observe such a “uniform” increase in the bandwidth persisting for >30 min. Baseline fetal heart rate variability (FHRV) on cardiotocography reflects the integrity of the central nervous system. During labor, in the presence of a gradually-evolving hypoxia associated with the onset of metabolic acidosis, FHRV may be reduced. However, if a fetus is exposed to rapidly-evolving hypoxia, it may not have sufficient time to release catecholamines and the perfusion of central organs can be impaired. In such cases, simultaneous increased activity of the sympathetic nervous system to obtain more oxygen as well as enhanced parasympathetic activity to reduce the myocardial workload can lead to autonomic instability. This exaggerated autonomic response can be seen frequently on the cardiotocograph as a rapid, irregular, abrupt “up and down” fluctuation across the baseline (amplitude >25 beats per min). The authors have termed this pattern as “ZigZag” when apparent for a minimum of 1 min. It differs from the SP in terms of duration and uniformity of the bandwidth. Objective: To determine the incidence of the SP during labor as well as a shorter and less uniform version of the SP newly called “ZigZag pattern” (ZZP). The intention was to correlate them with perinatal outcomes, taking into account the duration of the ZZP. Study design: A retrospective analysis of 500 consecutive cardiotocograph traces was performed to identify saltatory patterns and ZigZag patterns of 1 and 2 min of duration. Apgar scores, umbilical cord pH values and admission to the Neonatal Unit were evaluated and correlated with the cardiotocograph findings. Results: Not a single case of the SP was observed. A ZZP of 1 min of duration (ZZP1) was identified in 30.1% of the CTG during the last hour prior to delivery; ZZP lasting for 2 min (ZZP2) were identified in 8.9% of cases during the same period. Apgar scores at 1 min of ≤7 were significantly more frequent in newborns where the ZZP was observed (36.7% in ZZP1 and 54.5% in ZZP2 versus 9.5% in fetuses without); similarly, the Apgar scores at 5 min of ≤7 were also more frequent when ZZP was observed (6.7% in ZZP1 and 13.6% in ZZP2 versus 1.1% in controls). Moderate acidosis (pH 7.0–7.10) was more common in fetuses with the ZZP (14.3% in ZZP1 and 15% in ZZP2) compared to those without (4.6 and 7.2%, respectively). Similarly, mild acidosis (pH 7.1–7.2) was more common with the ZZP (40.3% in ZZP1 and 35% in ZZP2 versus 27.6 and 31.7%, respectively without ZZP). The neonatal admission rate was significantly higher in fetuses with the ZZP (8.7% in ZZP1 and 11.4% in ZZP2 versus 1.1% in controls). Conclusions: In line with previous research, our study suggest that SP is an almost nonexistent phenomenon. Alternatively, the ZigZag pattern (ZZP) has been defined as an exaggerated, irregular, “up and down” fluctuation of the baseline variability with an amplitude of >25 beats per min, lasting for 1 min or longer. It represents autonomic instability during human labor and it differs from the SP in terms of uniformity and length. Newborns with a ZZP during active maternal pushing were found to have statistically-significant lower Apgar scores at the 1st and 5th min, moderate and mild acidosis in the umbilical artery and an 8.7–11.4-fold higher neonatal admission rate. Clinicians should stop oxytocin infusion and/or active maternal pushing to improve fetal oxygenation if the ZZP is observed.

International expert consensus statement on physiological interpretation of cardiotocograph (CTG): First revision (2024)

Article

Full-text available

Oct 2024
EUR J OBSTET GYN R B

Pathophysiological interpretation of fetal heart rate tracings in clinical practice

Article

Jun 2023
AM J OBSTET GYNECOL

The onset of regular, strong, and progressive uterine contractions may result in both mechanical (compression of the fetal head and/or umbilical cord) and hypoxic (repetitive and sustained compression of the umbilical cord or reduction in uteroplacental oxygenation) stresses to a human fetus. Most fetuses are able to mount effective compensatory responses to avoid hypoxic-ischemic encephalopathy and perinatal death secondary to the onset of anaerobic metabolism within the myocardium, culminating in myocardial lactic acidosis. In addition, the presence of fetal hemoglobin, which has a higher affinity for oxygen even at low partial pressures of oxygen than the adult hemoglobin, especially increased amounts of fetal hemoglobin (ie, 180-220 g/L in fetuses vs 110-140 g/L in adults), helps the fetus to withstand hypoxic stresses during labor. Different national and international guidelines are currently being used for intrapartum fetal heart rate interpretation. These traditional classification systems for fetal heart rate interpretation during labor are based on grouping certain features of fetal heart rate (ie, baseline fetal heart rate, baseline variability, accelerations, and decelerations) into different categories (eg, category I, II, and III tracings, "normal, suspicious, and pathologic" or "normal, intermediary, and abnormal"). These guidelines differ from each other because of the features included within different categories and because of their arbitrary time limits stipulated for each feature to warrant an obstetrical intervention. This approach fails to individualize care because the "ranges of normality" for stipulated parameters apply to the population of human fetuses and not to the individual fetus in question. Moreover, different fetuses have different reserves and compensatory responses and different intrauterine environments (presence of meconium staining of amniotic fluid, intrauterine inflammation, and the nature of uterine activity). Pathophysiological interpretation of fetal heart rate tracing is based on the application of the knowledge of fetal responses to intrapartum mechanical and/or hypoxic stress in clinical practice. Both experimental animal studies and observational human studies suggest that, just like adults undertaking a treadmill exercise, human fetuses show predictable compensatory responses to a progressively evolving intrapartum hypoxic stress. These responses include the onset of decelerations to reduce myocardial workload and preserve aerobic metabolism, loss of accelerations to abolish nonessential somatic body movements, and catecholamine-mediated increases in the baseline fetal heart rate and effective redistribution and centralization to protect the fetal central organs (ie, the heart, brain, and adrenal glands), which are essential for intrauterine survival. Moreover, it is essential to incorporate the clinical context (progress of labor, fetal size and reserves, presence of meconium staining of amniotic fluid and intrauterine inflammation, and fetal anemia) and understand the features suggestive of fetal compromise in nonhypoxic pathways (eg, chorioamnionitis and fetomaternal hemorrhage). It is important to appreciate that the timely recognition of the speed of onset of intrapartum hypoxia (ie, acute, subacute, and gradually evolving) and preexisting uteroplacental insufficiency (ie, chronic hypoxia) on fetal heart rate tracing is crucial to improve perinatal outcomes.

Fetal heart rate monitoring in labor: From pattern recognition to fetal physiology

Article

Mar 2021

The journey of human labor involves hypoxic and mechanical stresses as a result of progressively increasing frequency, duration and strength of uterine contractions and resultant compression of the umbilical cord. in addition, occlusion of the spiral arteries during myometrial contractions also leads to repetitive interruptions in the utero-placental circulation, predisposing a fetus to progressively worsening hypoxic stress as labor progresses. the vast majority of fetuses are equipped with compensatory mechanisms to withstand these hypoxic and mechanical stresses. they emerge unharmed at birth. However, some fetuses may sustain an antenatal injury or experience a chronic utero-placental insufficiency prior to the onset of labor. these may impair the fetus to compensate for the ongoing hypoxic stress secondary to ongoing uterine contractions. Non-hypoxic pathways of neurological damage such as chorioamnionitis, fetal anemia or an acute fetal hypovolemia may potentiate fetal neurological injury, especially in the presence of a super-imposed, additional hypoxic stress. the use of utero-tonic agents to induce or augment labor may increase the risk of hypoxic-ischemic injury. Clinicians need to move away from "pattern recognition" guidelines ("normal," "suspicious," "pathological"), and apply the knowledge of fetal physiology to differentiate fetal compensation from decompensation. Individualization of care is essential to optimize outcomes.

Factors Associated with Intrapartum ZigZag Pattern of Fetal Heart Rate: A Retrospective One-Year Cohort Study of 5150 Singleton Childbirths

Article

Mar 2021
EUR J OBSTET GYN R B

Objectives: Recent studies suggest that intrapartum ZigZag pattern of fetal heart rate (FHR) is significantly associated with cord blood acidaemia and neonatal complications. For the clinical significance of this pattern, it is mandatory that ZigZag episodes in cardiotocographic (CTG) recording are correctly identified. The aim of the present study was to examine maternal, fetal and delivery-related factors that could explain the occurrence of ZigZag pattern of FHR during the last 2 hours of labour in a large obstetric cohort. Study design: CTG recordings from 5150 singleton childbirths at ≥33 weeks of gestation during one year were evaluated retrospectively and blinded to pregnancy and neonatal outcomes in a university hospital in Helsinki, Finland. All women in the cohort were in the active phase of labour with regular uterine contractions. ZigZag FHR pattern was defined as FHR baseline amplitude changes of >25 bpm with a duration of 2 – 30 minutes. The following maternal, fetal and labour/delivery-related variables were determined: maternal age, obesity (prepregnancy BMI ≥30.0 kg/m2), parity, preeclampsia, maternal fever ≥38.0 °C, smoking, gestational age at delivery, fetal sex, birth weight z-score, mode of delivery, and type of onset of labour. Results: ZigZag pattern occurred in 582/5150 (11.3%) cases, and only in childbirths after 37 weeks of gestation. Fetal male gender (OR 3.29; 95% CI 2.70–4.02), nulliparous pregnancy (OR 2.60; 95% CI 2.15–3.15) and post-term gestational age (≥42 weeks) (OR 1.92; 95% CI 1.47–2.48) were independently associated with the occurrence of ZigZag pattern. Among the three significant risk factors, clustering of two or three factors was associated with an increase of the ZigZag pattern occurrence risk to 5.0–16.4-fold (95% CI 3.16–31.60). Conclusions: ZigZag pattern occurred in term pregnancies after 37 weeks of gestation only. Fetal male gender, nulliparity and post-term pregnancy are significantly associated with ZigZag FHR pattern during the last two hours of labour. Identification of maternal, fetal and delivery-related variables are imperative in order to interpret correctly the findings of CTG and to prevent adverse neonatal outcome.

Intrapartum ZigZag Pattern of Fetal Heart Rate Is an Early Sign of Fetal Hypoxia: A Large Obstetric Retrospective Cohort Study

Article

Full-text available

Feb 2021

Introduction: The aim of the present study was to identify possible associations of fetal heart rate (FHR) patterns during the last 2 hours of labor with fetal asphyxia expressed by umbilical artery acidemia at birth and with neonatal complications in a large obstetric cohort. Material and methods: Cardiotocographic (CTG) recordings from 4988 singleton term childbirths during one year were evaluated retrospectively and blinded to the pregnancy and neonatal outcomes in a university teaching hospital in Helsinki, Finland. Umbilical artery (UA) pH, base excess (BE) and pO2, low Apgar scores at 5 minutes, need for intubation and resuscitation, early neonatal hypoglycemia, and neonatal encephalopathy were used as outcome variables. According to the severity of the neonatal complications at birth, the cohort was divided into three groups: no complications (Group 1), moderate complications (Group 2), and severe complications (Group 3). Results: Of the 4988 deliveries, ZigZag pattern (FHR baseline amplitude changes of >25 bpm with a duration of 2 – 30 minutes) occurred in 11.7%, late decelerations in 41.0%, bradycardia episodes in 52.9%, reduced variability in 36.7%, tachycardia episodes in 13.9%, and uterine tachysystole in 4.6%. Not a single case of saltatory pattern (baseline amplitude changes of >25 bpm with a duration of >30 minutes) was observed. The presence of ZigZag pattern or late decelerations, or both, was associated with cord blood acidemia (OR 3.3, 95% CI 2.3–4.7) and severe neonatal complications (Group 3) (OR 3.3, 95% CI 2.4–4.9). In contrast, no significant associations existed between the other FHR patterns and severe neonatal complications. ZigZag pattern preceded late decelerations in 88.7% of the cases. A normal FHR preceded the ZigZag pattern in 90.4% of the cases, whereas after ZigZag episodes a normal FHR pattern was observed in 0.9% only. Conclusions: ZigZag pattern and late decelerations during the last 2 hours of labor are significantly associated with cord blood acidemia at birth and neonatal complications. The ZigZag pattern precedes late decelerations, and the fact that normal FHR pattern precedes the ZigZag pattern in the majority of the cases suggests that ZigZag pattern is an early sign of fetal hypoxia, which emphasizes its clinical importance. Key Message: Intrapartum ZigZag pattern and late decelerations are significantly associated with cord blood acidemia and neonatal complications. ZigZag pattern precedes late decelerations in the majority of the cases and is an early sign of fetal hypoxia, which emphasizes its clinical importance.

Intrapartum ZigZag Pattern of Fetal Heart Rate Is an Early Sign of Fetal Hypoxia: A Large Obstetric Retrospective Cohort Study

Article

Full-text available

Oct 2020
ACTA OBSTET GYN SCAN

Introduction: The aim of the present study was to identify possible associations of fetal heart rate (FHR) patterns during the last 2 hours of labor with fetal asphyxia expressed by umbilical artery acidemia at birth and with neonatal complications in a large obstetric cohort. Material and methods: Cardiotocographic recordings from 4988 singleton term childbirths during one year were evaluated retrospectively and blinded to the pregnancy and neonatal outcomes in a university teaching hospital in Helsinki, Finland. Umbilical artery pH, base excess and pO2 , low Apgar scores at 5 minutes, need for intubation and resuscitation, early neonatal hypoglycemia, and neonatal encephalopathy were used as outcome variables. According to the severity of the neonatal complications at birth, the cohort was divided into three groups: no complications (Group 1), moderate complications (Group 2), and severe complications (Group 3). Results: Of the 4988 deliveries, ZigZag pattern (FHR baseline amplitude changes of >25 bpm with a duration of 2 - 30 minutes) occurred in 11.7%, late decelerations in 41.0%, bradycardia episodes in 52.9%, reduced variability in 36.7%, tachycardia episodes in 13.9%, and uterine tachysystole in 4.6%. Not a single case of saltatory pattern (baseline amplitude changes of >25 bpm with a duration of >30 minutes) was observed. The presence of ZigZag pattern or late decelerations, or both, was associated with cord blood acidemia (OR 3.3, 95% CI 2.3-4.7) and severe neonatal complications (Group 3) (OR 3.3, 95% CI 2.4-4.9). In contrast, no significant associations existed between the other FHR patterns and severe neonatal complications. ZigZag pattern preceded late decelerations in 88.7% of the cases. A normal FHR preceded the ZigZag pattern in 90.4% of the cases, whereas after ZigZag episodes a normal FHR pattern was observed in 0.9% only. Conclusions: ZigZag pattern and late decelerations during the last 2 hours of labor are significantly associated with cord blood acidemia at birth and neonatal complications. The ZigZag pattern precedes late decelerations, and the fact that normal FHR pattern precedes the ZigZag pattern in the majority of the cases suggests that ZigZag pattern is an early sign of fetal hypoxia, which emphasizes its clinical importance.

Computer Vision for Identification of Increased Fetal Heart Variability in Cardiotocogram

Article

Apr 2024

Introduction: Increased fetal heart rate variability (IFHRV), defined as fetal heart rate (FHR) baseline amplitude changes of >25 beats per minute with a duration of ≥1 min, is an early sign of intrapartum fetal hypoxia. This study evaluated the level of agreement of machine learning (ML) algorithms-based recognition of IFHRV patterns with expert analysis. Methods: Cardiotocographic recordings and cardiotocograms from 4,988 singleton term childbirths were evaluated independently by two expert obstetricians blinded to the outcomes. Continuous FHR monitoring with computer vision analysis was compared with visual analysis by the expert obstetricians. FHR signals were graphically processed and measured by the computer vision model labeled SALKA. Results: In visual analysis, IFHRV pattern occurred in 582 cardiotocograms (11.7%). Compared with visual analysis, SALKA recognized IFHRV patterns with an average Cohen’s kappa coefficient of 0.981 (95% CI: 0.972–0.993). The sensitivity of SALKA was 0.981, the positive predictive rate was 0.822 (95% CI: 0.774–0.903), and the false-negative rate was 0.01 (95% CI: 0.00–0.02). The agreement between visual analysis and SALKA in identification of IFHRV was almost perfect (0.993) in cases (N = 146) with neonatal acidemia (i.e., umbilical artery pH <7.10). Conclusions: Computer vision analysis by SALKA is a novel ML technique that, with high sensitivity and specificity, identifies IFHRV features in intrapartum cardiotocograms. SALKA recognizes potential early signs of fetal distress close to those of expert obstetricians, particularly in cases of neonatal acidemia.

Approaches to Preventing Intrapartum Fetal Injury

Article

Full-text available

Sep 2022

Electronic fetal monitoring (EFM) was introduced into obstetric practice in 1970 as a test to identify early deterioration of fetal acid-base balance in the expectation that prompt intervention (“rescue”) would reduce neonatal morbidity and mortality. Clinical trials using a variety of visual or computer-based classifications and algorithms for intervention have failed repeatedly to demonstrate improved immediate or long-term outcomes with this technique, which has, however, contributed to an increased rate of operative deliveries (deemed “unnecessary”). In this review, we discuss the limitations of current classifications of FHR patterns and management guidelines based on them. We argue that these clinical and computer-based formulations pay too much attention to the detection of systemic fetal acidosis/hypoxia and too little attention not only to the pathophysiology of FHR patterns but to the provenance of fetal neurological injury and to the relationship of intrapartum injury to the condition of the newborn. Although they do not reliably predict fetal acidosis, FHR patterns, properly interpreted in the context of the clinical circumstances, do reliably identify fetal neurological integrity (behavior) and are a biomarker of fetal neurological injury (separate from asphyxia). They provide insight into the mechanisms and trajectory (evolution) of any hypoxic or ischemic threat to the fetus and have particular promise in signaling preventive measures (1) to enhance the outcome, (2) to reduce the frequency of “abnormal” FHR patterns that require urgent intervention, and (3) to inform the decision to provide neuroprotection to the newborn.

Physiological interpretation of cardiotocograph (CTG): Inter-observer and “Observer-AI” agreements in recognising types of fetal hypoxic stress

Article

Full-text available

Dec 2024

Introduction: Interobserver reliability in interpreting cardiotocographs (CTGs) using traditional categorization into "normal," "suspicious," and "pathological" is typically very low ranging from Kappa 0.3 to 0.6. Physiological CTG interpretation focuses on identifying specific features of different types of fetal hypoxic stress and a combination of features which are associated with adverse perinatal outcomes. Objective To evaluate the agreement among members of the Editorial Board (EBM) of the international expert consensus statement on physiological CTG interpretation, members of the international expert consensus panel (ICP), and the Tweris Mini App (TMA), which is an AI-based CTG interpretation tool developed based on international expert consensus statement. Materials & Methods: Thirty 10–15-minute CTG trace segments, representing different types of fetal hypoxic stress (chronic, gradually evolving compensated, gradually evolving decompensated, subacute, and acute) and abnormal CTG patterns (atypical sinusoidal or the “Poole Shark Teeth”, typical sinusoidal and the ZigZag patterns), were independently reviewed by 3 editorial board members and 3 international expert consensus panel members. An orthopedic surgeon independently analyzed the same traces using the TMA. Fleiss' Kappa and Z-scores were used for statistical analysis. Results: Inter-observer agreement was 0.8 (95% CI: 0.72-0.87, p < .001) among EBM and 0.68 (95% CI: 0.60-0.76, p < .001) among ICP, with a statistically significant difference between these groups (p < .05). Agreement between EBM and the Tweris Mini App was higher than between ICP and the Tweris Mini App (0.81 vs 0.73, p = .06). Conclusion: The inter-observer agreement when using physiological CTG interpretation surpasses that of the inter-observer agreement reported with traditional systems of CTG classification, with higher interobserver agreement among editorial board members compared to international expert consensus panel members. There was a substantial agreement between editorial board members and the Tweris Mini app which was higher than between ICP and the Tweris Mini App. These findings highlight the potential of AI-assisted tools, such as the Tweris Mini App, based on physiological CTG interpretation, to provide expert-level diagnostic accuracy in clinical practice. The Tweris Mini App was found to be superior in consistently recognising rare fetal heart rate patterns.

Analysis of CTG patterns in cases with metabolic acidosis at birth with and without neonatal neurological alterations

Article

Full-text available

Jan 2024

Objective To determine cardiotocographic patterns in newborns with metabolic acidosis, based on clinical signs of neurological alteration (NA) and the need for hypothermic treatment. Methods All term newborns with metabolic acidosis in a single center from 2016 to 2020 were included in the study. Three segments of intrapartum CTG (cardiotocography) were considered (first 30 min of active labor, 90 to 30 min before birth, and last 30 min before delivery) and a longitudinal analysis of CTG pattern was performed according to the 2015 FIGO classification. Results Three hundred and twenty-four neonates with metabolic acidosis diagnosed at birth were divided into three groups: the first group included all neonates with any clinical sign of neurological alteration, requiring hypothermia according to the recommendation of the Italian Society of Neonatology (group TNA—Treated neurological Alteration, n = 17), the second encompassed neonates with any clinical sign of neurological alteration not requiring hypothermia (group NTNA—Not Treated neurological Alteration, n = 83), and the third enclosed all neonates without any sign of clinical neurological involvement (group NoNA—No neurological Alteration, n = 224). The most frequent alterations of CTG in TNA group were late decelerations, reduced variability, bradycardia, and tachysystole. Unexpectedly, from the longitudinal analysis of the CTG, 49% of all cases with metabolic acidosis never showed a pathological CTG with normal trace at the beginning of labor followed by normal or suspicious trace in the final part of labor, the same as in TNA and NTNA groups (10 and 39%, respectively). Conclusions CTG has limited specificity in identifying cases of acidosis at birth, even in babies who will develop NA.

Updated NICE Cardiotocograph (CTG) Guideline: Is it Suspicious or Pathological?

Article

Full-text available

Jan 2024

Edwin Chandraharan

Cardiotocograph (CTG) trace was introduced into clinical practice in 1960s as a tool to record the changes in the fetal heart rate (cardio) in response to ongoing uterine contractions (toco). The intention was to timely recognise the features of fetal decompensation so that immediate action could be taken to avoid hypoxic ischaemic encephalopathy (HIE) and/ or intrapartum hypoxia-related perinatal deaths, without increasing unnecessary operative interventions to the mother. However, very unfortunately, unlike other tools in clinical medicine, CTG was introduced into clinical practice without any randomised controlled trials or robust scientific studies not only to confirm its effectiveness, but to determine the CTG features which actually reflected fetal central organ oxygenation. This chasm of deficiency of knowledge of fetal physiology created a vacuum of understanding regarding what features were reflecting fetal compromise. Regrettably, this vacuum was soon filled by prominent obstetricians from national societies who were presumed to have the knowledge, but they began the arduous journey of classifying decelerations which are normal fetal cardioprotective reflexes, and they misclassified them as signs of "fetal distress". Classification of these decelerations based on the observed morphology into "reassuring" and "nonreasoning" categories has resulted in disastrous consequences for women and babies. In the UK, since the publication of the first CTG guideline in 2001, due to continuing lack of knowledge and confusion, these guidelines were repetitively revised in 2007, 2014, 2017 and 2022. Despite the international consensus guidelines of physiological interpretation of CTG produced by 44 CTG experts from 14 countries which recommended classification of CTG traces based on the type of fetal hypoxia and fetal response to stress, the lat-est revised guideline produced by the National Institute of Health and Care Excellence (NICE), had continued the illogical approach of grouping arbitrary features into different categories and then randomly combining them to classify the CTG traces into "Normal, Suspicious and Pathological". Therefore, all practising clinicians who are focussed on protecting their patients from harm have a responsibility to ask the question whether the revised NICE CTG Guideline itself is suspicious or pathological from a patient safety perspective.

Is the fetus fit for labor? Introducing fast‐and‐frugal trees (FFTrees) to simplify triage of women for STAN monitoring: An interobserver agreement comparison with traditional classification

Article

Full-text available

Oct 2023
ACTA OBSTET GYN SCAN

Introduction It is a shortcoming of traditional cardiotocography (CTG) classification table formats that CTG traces are frequently classified differently by different users, resulting in poor interobserver agreements. A fast‐and‐frugal tree (FFTree) flow chart may help provide better concordance because it is straightforward and has clearly structured binary questions with understandable “yes” or “no” responses. The initial triage to determine whether a fetus is suitable for labor when utilizing fetal ECG ST analysis (STAN) is very important, since a fetus with restricted capacity to respond to hypoxic stress may not generate STAN events and therefore may become falsely negative. This study aimed to compare physiology‐focused FFTree CTG interpretation with FIGO classification for assessing the suitability for STAN monitoring. Material and methods A retrospective study of 36 CTG traces with a high proportion of adverse outcomes (17/36) selected from a European multicenter study database. Eight experienced European obstetricians evaluated the initial 40 minutes of the CTG recordings and judged whether STAN was a suitable fetal surveillance method and whether intervention was indicated. The experts rated the CTGs using the FFTree and FIGO classifications at least 6 weeks apart. Interobserver agreements were calculated using proportions of agreement and Fleiss’ kappa (κ). Results The proportions of agreement for “not suitable for STAN” were for FIGO 47% (95% confidence interval [CI] 42%–52%) and for FFTree 60% (95% CI 56–64), ie a significant difference; the corresponding figures for “yes, suitable” were 74% (95% CI 71–77) and 70% (95% CI 67–74). For “intervention needed” the figures were 52% (95% CI 47–56) vs 58% (95% CI 54–62) and for “expectant management” 74% (95% CI 71–77) vs 72% (95% CI 69–75). Fleiss’ κ agreement on “suitability for STAN” was 0.50 (95% CI 0.44–0.56) for the FIGO classification and 0.57 (95% CI 0.51–0.63) for the FFTree classification; the corresponding figures for “intervention or expectancy” were 0.53 (95% CI 0.47–0.59) and 0.57 (95% CI 0.51–0.63). Conclusions The proportion of agreement among expert obstetricians using the FFTree physiological approach was significantly higher compared with the traditional FIGO classification system in rejecting cases not suitable for STAN monitoring. That might be of importance to avoid false negative STAN recordings. Other agreement figures were similar. It remains to be shown whether the FFTree simplicity will benefit less experienced users and how it will work in real‐world clinical scenarios.

Fetal Electrocardiograph (ST-Analyser or STAN): Is it time for the Requiem?

Article

Full-text available

Aug 2023

Edwin Chandraharan

Cardiotocograph (CTG) was introduced into clinical practice to timely recognise features of the onset of decompensation so that timely action could be taken to avoid hypoxic-ischaemic encepha-lopathy (HIE) or perinatal deaths. Unfortunately, systematic reviews have shown that classification of CTG traces into "normal, suspicious and pathological" (or "Category I, II and III in the USA) has not only failed to reduce intrapartum operative interventions, cerebral palsy and perinatal deaths, but it was also associated with significant inter-and interobserver variability. Fetal electrocardiograph (ECG) or ST-analysis (STAN) was introduced into clinical practice to reduce the false positive rate of cardiotocograph (CTG) and to reduce the rate of unnecessary intrapartum operative interventions such as emergency caesarean sections, vacuum and forceps births. Although the STAN technology is based on sound physiological principles, its Achilles' Heel is the continued use of the CTG classification tool using "normal, intermediary and abnormal" by arbitrarily grouping several features into different categories without any robust scientific evidence. This exposes the STAN technology to the same flaws of "pattern-recognition" and inter-and intra-observer variability. In the light of recent systematic reviews and meta-analysis showing no benefit in reducing emergency caesarean section and the most recent randomised controlled trial from Australia suggesting that introduction of STAN technology as an adjunct to CTG has failed to show any reduction in intrapartum operative interventions , frontline clinicians have to ask the question: Is it time for the Requiem for STAN? Link https://www.jclinmedsurgery.com/articles/jcms-v3-1111.html

Physiological Interpretation of Cardiotocograph: Does the Emerging Scientific Evidence Suggest a Reversal in the "Thunder and Lightning" Phenomenon? Journal of Clinical & Medical Surgery

Article

Full-text available

May 2023

Physiological interpretation of Cardiotocograph (CTG) involves incorporation of the knowledge of fetal physiological response to intrapartum hypoxic and mechanical stresses and diagnosing different types of fetal hypoxia, to individualise care. It advocates two key questions whilst interpreting CTG traces: "Is THIS fetus FIT to undertake the progressively hypoxic journey of labour?" at the beginning of the recording , and "How is THIS fetus?" during labour. Therefore, it differs from other national and international CTG guidelines which arbitrarily group several "features" of the fe-tal heart rate into different "categories" (reassuring, non-reassuring and abnormal), and then having an overall classification system by randomly grouping 2 "non-reas-suring' features as "suspicious", and two or more "non-reassuring features or one or more "abnormal" features as "pathological" without incorporating fetal physiological responses. Fortunately, most clinical guidelines are evidence-based and logical, and therefore their implementation (lightening) happens first, and changes in clinical practice (thunder) follows this to improve outcomes. However, in rare occasions where, unfortunately, continuation of historical, and entrenched, unscientific cultural practices are likely to cause patient harm, clinical practice may need to change first to safeguard patients, followed by the production of appropriate clinical guidelines based on emerging scientific evidence.

Emergency Cesarean Section in the Intensive Care Unit for a Woman with Severe Preeclampsia and Coronavirus Disease 2019: A Case Report

Article

Full-text available

Jan 2023

Introduction of the Physiological CTG Interpretation & Hypoxia in Labour (HIL) Tool, and its Incorporation into a Software Programme: Impact on Perinatal Outcomes

Article

Full-text available

Jun 2021

Edwin Chandraharan

Uterine Tachysystole, Hypertonus and Hyperstimulation: An Urgent Need to get the Definitions Right to Avoid Intrapartum Hypoxic-Ischemic Brain Injury

Article

Full-text available

Apr 2021

Edwin Chandraharan

Intrapartal cardiotocographic patterns and hypoxia-related perinatal outcomes in pregnancies complicated by gestational diabetes mellitus

Article

Full-text available

Jun 2021

Aims In previous reports, cardiotocographic (CTG) fetal heart rate (FHR) monitoring has shown only limited benefits in decreasing adverse perinatal outcomes in pregnancies complicated by gestational diabetes mellitus (GDM). The aim of the present study was to evaluate whether an association exists between the recently reported ZigZag pattern (FHR baseline amplitude changes of > 25 bpm with a duration of 2–30 min) and asphyxia-related neonatal outcomes in GDM pregnancies. Methods Intrapartal CTGs were recorded in a one-year cohort of 5150 singleton childbirths. The following CTG changes were evaluated: ZigZag pattern, saltatory pattern, late decelerations, episodes of tachycardia and bradycardia, reduced variability, and uterine tachysystole. The cohort was divided into three groups: women with GDM, women with normal oral glucose tolerance test (OGTT), and women with no OGTT performed. Umbilical artery (UA) blood gases, Apgar scores, neonatal respiratory distress, and neonatal encephalopathy were used as outcome variables. Results GDM was diagnosed in 624 (12.1%), OGTT was normal in 4115 (79.9%), and OGTT was not performed in 411 (8.0%) women. Hypoxia-related ZigZag patterns (OR 1.94, 95% CI 1.64–2.34) and late decelerations (OR 1.65, 95% CI 1.27–2.13) of FHR, as well as a greater risk of fetal asphyxia (UA pH < 7.10 and/or UA BE < -12.0 meq/L and/or Apgar scores < 7 at 5-min) (OR 6.64, 95% CI 1.84–12.03) were observed in those with GDM compared with those without GDM. Conclusions GDM is associated with intrapartal ZigZag pattern and late decelerations, cord blood acidemia and low 5-min Apgar scores at birth indicating increased occurrence of fetal hypoxia in GDM pregnancies.

Uterine Tachysystole, Hypertonus and Hyperstimulation: An urgent need to get the definitions right to avoid Intrapartum Hypoxic-Ischaemic Brain Injury

Article

Full-text available

Apr 2021

Cardiotocograph (CTG) changes and Maternal and neonatal outcomes in Chorioamnionitis and/or Funisitis confirmed on histopathology

Article

Mar 2021
EUR J OBSTET GYN R B

Objective To assess the cardiotocographic changes and maternal and neonatal outcomes in cases of chorioamnionitis and or funisitis confirmed on histopathology. Study Design A retrospective analysis of histopathology reports confirming chorioamnionitis and/or funisitis was carried out from 2014 -2020 in a single centre. The preterm births (<37 weeks) were excluded. The maternal records were reviewed to determine the maternal and neonatal outcomes such as the mode of delivery, intrapartum and postpartum complications, umbilical cord arterial pH, and admission to the special care baby unit (SCBU). The CTG features were analysed on admission and during the intrapartum period. The study was approved by the Audit and Clinical Effectiveness department within the centre. Results Out of the 57 cases of histologically confirmed chorioamnionitis and/or funisitis, 42 women (73.7%) had intrapartum pyrexia and none of the mothers had an increased temperature at the point of fetal tachycardia (persistent increase in baseline fetal heart rate (FHR) by >10 % compared to the original baseline FHR). 43 (75.4%) CTGs showed evidence of uterine tachysystole or hyperstimulation. 15 (26.3%) cases had meconium stained amniotic fluid (MSAF). 54 (94.7%) women had a caesarean section, and their babies were admitted to special care baby unit after delivery. 54 (94.7%) babies had an umbilical artery of more than 7.1. 47 (87%) of the women were readmitted with wound infection. All CTG traces showed a > 10% increase in the baseline FHR and variable decelerations with overshoot were noted in cases where funisitis was confirmed in 25 cases (92.6%). Loss of cycling was noted in 54 CTGs (94.7%) and a sinusoidal pattern was identified in 27 (47.3%). Conclusion Rising (>10%) baseline during labour along with loss of cycling with or without features of tachysystole or hyperstimulation should be considered in labour as features of ongoing chorioamnionitis. Chorioamnionitis confirmed on histopathology is associated with an increase in caesarean section rate due to fetal heart rate changes, increased risk of wound infection in mothers, and increased admission of the babies to SCBU.

Fetal heart rate changes on the cardiotocograph trace secondary to maternal COVID-19 infection

Article

Jul 2020
EUR J OBSTET GYN R B

Objective To determine the cardiotocograph (CTG) changes in women with symptomatic COVID-19 infection. Study design 12 anonymised CTG traces from 2 hospitals in Spain were retrospectively analysed by 2 independent assessors. CTG parameters were studied based on fetal pathophysiological responses to inflammation and hypoxia that would be expected based on the pathogenesis of COVID-19 patients. Correlation was made with perinatal outcomes (Apgar score at 5 minutes and umbilical cord pH). Results All fetuses showed an increased baseline FHR > 10 percent compared to the initial recording, in addition to absence of accelerations. 10 out of 12 CTG traces (83.3 percent) demonstrated late or prolonged decelerations and 7 out of 12 fetuses (58.3 percent) showed absence of cycling. Not a single case of sinusoidal pattern was observed. ZigZag pattern was found in 4 CTG traces (33 percent). Excessive uterine activity was observed in all CTG traces where uterine activity was monitored (10 out of 12). Apgar scores at 5 minutes were normal (>7) and absence of metabolic acidosis was found in the umbilical cord arterial pH (pH > 7.0) in the cases that were available (11 and 9, respectively). Conclusion Fetuses of COVID-19 patients showed a raised baseline FHR (>10 percent), loss of accelerations, late decelerations, ZigZag pattern and absence of cycling probably due to the effects of maternal pyrexia, maternal inflammatory response and the “cytokine storm”. However, the perinatal outcomes appear to be favourable. Therefore, healthcare providers should optimise the maternal environment first to rectify the reactive CTG changes instead of performing an urgent operative intervention.

Perinatal outcomes in fetuses with cardiotocography (CTG) changes suggestive for chorioamnionitis

Article

Mar 2019
EUR J OBSTET GYN R B

Rational approach to fetal heart rate monitoring and management during the second stage of labor

Article

Dec 2024
EUR J OBSTET GYN R B

Second stage of labor is considered to be associated with an increased risk of intrapartum fetal hypoxic injury. This is due to a combination of several risk factors such as -the increased frequency, strength and duration of uterine contractions due to higher number and affinity of myometrial oxytocin receptors; -the Ferguson’s reflex which leads to a reflex release of endogenous oxytocin in response of the distension of the cervix by descending fetal head in late stages of labor; maternal expulsive efforts with the Valsalva manoeuvre that may reduce maternal oxygenation, as well as reduce the venous return and maternal cardiac output due to increased intrathoracic pressure, winch may lead to reduced placental oxygenation; - and increased fetal intracranial pressure due to head compression leading to a potential decrease in fetal cerebral oxygenation. In addition, the umbilical cord often forms one or more loops around the fetal neck, which may get tightened as the head descends leading to an acute and intermittent cessation of fetal oxygenation. Operative interventions during the second stage of labor such as vacuum, forceps or emergency caesarean section may increase the risk of maternal and fetal trauma. Therefore, an accurate interpretation of the fetal heart rate changes by applying the knowledge of fetal pathophysiology is essential: to timely recognise the onset of fetal decompensation preventing intrapartum hypoxic-ischaemic brain injuries; to avoid erroneous monitoring of the maternal heart rate as fetal heart rate; and to abstain from unnecessary operative interventions due to misinterpretation of the significance of the observed fetal heart rate changes. Key Words: Subacute hypoxia; ZigZag pattern; Double Mountain Peak Sign; tocolysis; Ferguson’s Reflex.

Case Report: Peripartum periventricular leukomalacia resulting in cerebral palsy associated with placenta previa in Japan

Article

Full-text available

Aug 2024

Shunji Suzuki

Intrapartum fetal heart rate monitoring abnormalities had been reported to correlate with decreased umbilical artery base excess associated with neonatal seizures. However, we present an infant born at 35 weeks of gestation diagnosed with cerebral palsy associated with periventricular leukomalacia (PVL) without fetal heart rate (FHR) monitoring abnormalities, According to the summary reports of PVL cases published on the home page of the Japan Obstetric Compensation System for Cerebral Palsy (JOCSC)), the percentage of placenta previa without FHR monitoring abnormalities in the cases of PVL was 5.7% (12/209), which seemed to be higher than the total percentage of placenta previa reported in Japan (0.3–0.5%).

Fetal Compromise: Diagnosis and Management

Chapter

Jun 2021

Global and national confidential inquiry reports show that 60 to 80% of maternal and neonatal morbidity and mortality are due to avoidable errors. This comprehensive and illustrated second edition offers a practical guide to the management of obstetric, medical, surgical, anaesthetic and newborn emergencies in addition to organisational and training issues. The book is divided conveniently into nine sections and updated throughout in line with modern research and practice. Several new chapters cover setting up skills and drills training in maternity services to reduce avoidable harm, managing obstetric emergencies during 'home births' and in low-risk midwifery units, and minimizing maternal and fetal morbidity in failed operative vaginal delivery. Each chapter includes a practical algorithm for quick reference, the scientific basis for proposed actions, a case-based practical exercise and useful learning tools such as 'Key Pearls' and 'Key Pitfalls'. An invaluable resource for obstetricians, neonatologists, midwives, medical students, anesthesiologists and the wider perinatal team.

Intrapartum fetal surveillance: a physiological approach

Article

Jun 2022
Obstet Gynaecol Reprod Med

Continuous utero-placental circulation, and patent umbilical blood vessels ensure an uninterrupted transfer of oxygen and nutrients to the fetus as well as clearance of metabolic waste products. The onset of labour characterized by progressive and strong uterine contractions poses a threat to fetal oxygenation as a result of collapsing the spiral arterioles traversing the myometrium to supply the placental bed, and repetitive compression of the blood vessels within the umbilical cord. Human fetuses are equipped with compensatory mechanisms to cope with transient interruptions of blood supply during labour. The ability to compensate may be blunted in cases of poor fetal reserves, increased metabolic demand (macrosomia or maternal fever), and due to non-hypoxic pathways (e.g. chorioamniontis or fetal hypovolumia-hypotension syndrome). Intrapartum fetal surveillance involves prompt recognition of the features that signal the onset of fetal decompensation on the cardiotocograph (CTG) to ensure a timely intervention to avoid hypoxic-ischaemic encephalopathy (HIE) or perinatal deaths. This article summarises a ‘physiological approach’ to the interpretation of the CTG which, in places, conflicts with other current UK guidance.

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Article

Full-text available

Jun 2022
BJOG-INT J OBSTET GY

Increased fetal heart rate variability (FHRV) in intrapartum cardiotocographic recording has been variably defined and poorly understood, limiting its clinical utility. Both preclinical (animal) and clinical (human) evidence support that increased FHRV is observed in the early stage of intrapartum fetal hypoxaemia but can also be observed in a subset of fetuses during the preterminal stage of repeated hypoxaemia. This review of available evidence provides data and expert opinion on (1.) pathophysiology of increased FHRV, (2.) its clinical significance, and (3.) a stepwise approach regarding the management of this pattern and (4.) propose recommendations for standardisation of related terminology.

Prediction of Neonatal Acidosis Based on the Type of Fetal Hypoxia Observed on the Cardiotocograph (CTG)

Article

Full-text available

Apr 2022

Cardiotocograph (CTG) was introduced into clinical practice to promptly recognize the features of intrapartum fetal hypoxic stress, so that timely action could be taken to avoid hypoxic-ischaemic encephalopathy (HIE) and perinatal deaths. However, the current systematic evidence suggests that the introduction of CTG into clinical practice over 50 years has not resulted in improvement in the rates of cerebral palsy or perinatal deaths. This is because most fetuses are able to withstand intrapartum hypoxic stresses without sustaining damage, and if the features of fetal compensatory responses are erroneously considered as “pathological”, “Abnormal” or “Category III” CTG tracing, it would lead to an exponential increase in unnecessary operative interventions without any improvement in perinatal outcomes. Neonatal acidosis at birth, determined by the estimation of pH in the umbilical artery has been considered as a surrogate marker of poor perinatal outcome. This is because significant intrapartum fetal hypoxic stress which leads to fetal decompensation, would lead to the onset of anaerobic metabolism and production of lactic acid in fetal tissues and organs. Entry of lactic acid into the fetal systemic circulation may cause damage to fetal central organs resulting in organ damage and death, and this lactate may lower the pH in the umbilical artery. Understanding the different types of fetal hypoxia on the CTG trace may help practicing clinicians to predict the rate of fall in fetal pH, and therefore, predict the umbilical cord pH at birth. It is important to appreciate that non-hypoxic pathways of fetal compromise such as chorioamnionitis may not be associated with low umbilical arterial pH at birth. Fetal pathophysiological approach to CTG interpretation based on deeper understanding of types of intrapartum hypoxia and features of non-hypoxic pathways of injury may help avoid the onset of neonatal metabolic acidosis and improve perinatal outcomes.

Physiological control of fetal heart rate variability during labour: implications and controversies

Article

Full-text available

Jan 2022
J PHYSIOL-LONDON

The interpretation of fetal heart rate (FHR) patterns is the only available method to continuously monitor fetal well‐being during labour. One of the most important yet contentious aspects of the FHR pattern is changes in FHR variability (FHRV). Some clinical studies suggest that loss of FHRV during labour is a sign of fetal compromise so this is reflected in practice guidelines. Surprisingly, there is little systematic evidence to support this observation. In this review we methodically dissect the potential pathways controlling FHRV during labour‐like hypoxaemia. Before labour, FHRV is controlled by the combined activity of the parasympathetic and sympathetic nervous systems, in part regulated by a complex interplay between fetal sleep state and behaviour. By contrast, preclinical studies using multiple autonomic blockades have now shown that sympathetic neural control of FHRV was potently suppressed between periods of labour‐like hypoxaemia, and thus, that the parasympathetic system is the sole neural regulator of FHRV once FHR decelerations are present during labour. We further discuss the pattern of changes in FHRV during progressive fetal compromise and highlight potential biochemical, behavioural and clinical factors that may regulate parasympathetic‐mediated FHRV during labour. Further studies are needed to investigate the regulators of parasympathetic activity to better understand the dynamic changes in FHRV and their true utility during labour. image

Cardiotocographic features in COVID-19 infected pregnant women

Article

Full-text available

Aug 2021

Objectives We aimed to evaluate the cardiotocograph (CTG) traces of 224 women infected with novel coronavirus 2019 (COVID-19) and analyze whether changes in the CTG traces are related to the severity of COVID-19. Methods We designed a prospective cohort study. Two-hundred and twenty-four women who had a single pregnancy of 32 weeks or more, and tested positive for SARS-CoV-2 were included. Clinical diagnosis and classifications were made according to the Chinese management guideline for COVID-19 (version 6.0). Patients were classified into categories as mild, moderate, severe and the CTG traces were observed comparing the hospital admission with the third day of positivity. Results There was no statistically significant relationship between COVID-19 severity and CTG category, variability, tachycardia, bradycardia, acceleration, deceleration, and uterine contractility, Apgar 1st and 5th min. Conclusions Maternal COVID-19 infection can cause changes that can be observed in CTG. Regardless of the severity of the disease, COVID-19 infection is associated with changes in CTG. The increase in the baseline is the most obvious change.

Handbook of CTG Interpretation: From Patterns to Physiology

Book

Full-text available

Feb 2017

Edwin Chandraharan

Fetal heart rate changes observed on the CTG trace during instrumental vaginal delivery

Article

Full-text available

Sep 2017

Introduction: Instrumental vaginal delivery (IVD) helps expedite delivery during second stage of labour so as to avoid a second stage caesarean section. However, due to mechanical effects on the fetal head, vacuum and forceps may cause cardiotocograph (CTG) abnormalities due to vigal stimulation as well as increased intracranial pressure. Objective: To determine the features observed on the CTG during IVD in term pregnancy and correlate them to perinatal outcomes. Methods: A retrospective analysis of 445 cases who had vacuum deliveries (227) and forceps deliveries (218) at St. George’s University Hospitals NHS Foundation Trust during a 12-month period was performed. CTG features were analysed at 10 minutes prior to and immediately after applications of the chosen instrument till delivery. Specific abnormalities were correlated to Apgar score and umbilical blood pH. Results: Specific CTG abnormalities after applications of vacuum and forceps were: tachycardia (99 (43.61%) versus 88 (40.37%)), increased baseline fetal heart rate (FHR) [14 (6.17%) versus 4 (1.83%) p = .0204], baro-receptor-mediated “variable” deceleration (101 (44.49%) versus 85 (38.99%)), chemoreceptor-mediated “late” deceleration (62 (27.31%) versus 76 (34.86%)), prolonged deceleration (32 (14.10%) versus 24 (11.01%)), saltatory pattern [35 (15.42%) versus 76 (34.86%) p < .0001], and reduced baseline variability (10 (4.41%) versus 7 (3.21%)). There were no significant differences in the mean Apgar Scores at 1 and 5 minutes between ventouse and forceps delivery (8 and 9, respectively) or the umbilical blood pH (both >7.20). Conclusions: After application of instruments, 90% of CTG traces showed abnormal features. Tachycardia, baro- and chemoreceptor-mediated decelerations, and saltatory patterns were the most common abnormalities. Increased baseline FHR during vacuum as compared to forceps delivery was possibly secondary to pain/pressure and resultant sympathetic overactivity. The saltatory pattern was more common in forceps deliveries, possibly secondary to increased intracranial pressure and resultant autonomic instability. Despite these CTG abnormalities, the perinatal outcomes were good.

FIGO consensus guidelines on intrapartum fetal monitoring: Intermittent auscultation

Article

Full-text available

Oct 2015

Intermittent auscultation is the technique used to listen to the fetal heart rate (FHR) for short periods of time without a display of the resulting pattern. Whether it is used for intrapartum fetal monitoring in low-risk women or for all cases in settings where there are no available alternatives, all healthcare professionals attending labor and delivery need to be skilled at performing intermittent auscultation, interpreting its findings, and taking appropriate action. The main aim of this chapter is to describe the tools and techniques for intermittent auscultation in labor.

FIGO consensus guidelines on intrapartum fetal monitoring: Cardiotocography

Article

Full-text available

Oct 2015

The purpose of this chapter is to assist in the use and interpretation of intrapartum cardiotocography (CTG), as well as in the clinical management of specific CTG patterns. In the preparation of these guidelines, it has been assumed that all necessary resources, both human and material, required for intrapartum monitoring and clinical management are readily available. Unexpected complications may occur during labor, even in patients without prior evidence of risk, so maternity hospitals need to ensure the presence of trained staff, as well as appropriate facilities and equipment for an expedite delivery (in particular emergency cesarean delivery). CTG monitoring should never be regarded as a substitute for good clinical observation and judgement, or as an excuse for leaving the mother unattended during labor.

Prolonged saltatory fetal heart rate pattern leading to newborn metabolic acidosis

Article

Full-text available

Oct 2014

The saltatory pattern, characterized by wide and rapid oscillations of the fetal heart rate (FHR), remains a controversial entity. The authors sought to evaluate whether it could be associated with an adverse fetal outcome. The authors report a case series of four saltatory patterns occurring in the last 30 minutes before birth in association with cord artery metabolic acidosis, obtained from three large databases of internally acquired FHR tracings. The distinctive characteristics of this pattern were evaluated with the aid of a computer system. All cases were recorded in uneventful pregnancies, with normal birthweight singletons, born vaginally at term. The saltatory pattern lasted between 23 and 44 minutes, exhibited a mean oscillatory amplitude of 45.9 to 80.0 beats per minute (bpm) and a frequency between four and eight cycles per minute. A saltatory pattern exceeding 20 minutes can be associated with the occurrence of fetal metabolic acidosis.

The role of the neural sympathetic and parasympathetic systems in diurnal and sleep state-related cardiovascular rhythms in the late-gestation ovine fetus

Article

Full-text available

Jul 2009
AM J PHYSIOL-REG I

The efferent mechanisms mediating the well-known diurnal cardiovascular rhythms in the late-gestation fetus are only partially understood. In the present study, we evaluated the contribution of the parasympathetic and sympathetic nervous systems (SNS) to these rhythms. Chronically instrumented fetal sheep at a mean (SE) of 122 (1) days gestation (term is 147 days) underwent either chemical sympathectomy with 6-hydroxydopamine the day after surgery (n = 8), vagotomy at surgery (n = 8), or were sham controls (n = 8). Fetal heart rate (HR), fetal HR variability (HRV), mean arterial blood pressure (MAP), carotid blood flow (CaBF), electrocorticogram (ECoG) activity, and nuchal activity were measured continuously for 24 h. Changes between sleep states were determined in a 6-h interval. Control fetal sheep showed consistent diurnal rhythms in fetal HR, HRV, MAP, and CaBF, with maximal activity in the evening, but not in nuchal activity. Sympathectomy was associated with a significant reduction of both fetal HR and HRV, while vagotomy was associated with a fall in fetal HRV (P < 0.05) but no change in HR. Despite this, most animals in the two intervention groups still showed diurnal rhythms for fetal HR, HRV, MAP, and CaBF, although peak HR may have been delayed in the sympathectomy group (mean 02:22 vs. 23:54 h in controls, P = 0.06). There was no effect of either intervention on sleep state cycling, although state-related cardiovascular rhythms were significantly modulated. These data indicate that, neither the SNS nor vagal activity, in isolation at least, is essential for generating cardiovascular diurnal rhythms in the late-gestation fetus.

Development of the fetal cardiovascular defence to hypoxemia towards term

Article

Full-text available

Dec 2006

We tested the hypothesis that fetal cardiovascular responses to hypoxemia change close to full term in relation to the prepartum increase in fetal basal cortisol and investigated, in vivo, the neural and endocrine mechanisms underlying these changes. Fetal heart rate and peripheral hemodynamic responses to 1 h of hypoxemia were studied in 25 chronically instrumented sheep within three narrow gestational age ranges: 125-130 (n = 13), 135-140 (n = 6), and >140 (n = 6) days (full term approximately 145 days). Chemoreflex function and plasma concentrations of vasoconstrictor hormones were measured. Reductions in fetal arterial Po(2) during hypoxemia were similar at all ages. At 125-130 days, hypoxemia elicited transient bradycardia, femoral vasoconstriction, and increases in plasma concentrations of catecholamines, neuropeptide Y (NPY), AVP, ACTH, and cortisol. Close to full term, in association with the prepartum increase in fetal basal cortisol, there was a developmental increase in the magnitude and persistence of fetal bradycardia and in the magnitude of the femoral constrictor response to hypoxemia. The mechanisms mediating these changes close to full term included increases in the gain of chemoreflex function and in the magnitudes of the fetal NPY and AVP responses to hypoxemia. Data combined irrespective of gestational age revealed significant correlations between fetal basal cortisol and fetal bradycardia, femoral resistance, chemoreflex function, and plasma AVP concentrations. The data show that the fetal cardiovascular defense to hypoxemia changes in pattern and magnitude just before full term because of alterations in the gain of the neural and endocrine mechanisms mediating them, in parallel with the prepartum increase in fetal basal cortisol.

FHR patterns that become significant in connection with ST waveform changes and metabolic acidosis at birth

Article

Apr 2018

Introduction: Recent developments have produced new CTG classification systems and the question is to what extent these may affect the model of FHR + ST interpretation? The two new systems (FIGO2015 and SSOG2017) classify FHR+ ST events differently from the current CTG classification system used in the STAN interpretation algorithm (STAN2007). Aim: Identify the predominant FHR patterns in connection with ST events in cases of cord artery metabolic acidosis missed by the different CTG classification systems. Indicate to what extent STAN clinical guidelines could be modified enhancing the sensitivity. Provide a pathophysiological rationale. Material and methods: Forty-four cases with umbilical cord artery metabolic acidosis were retrieved from a European multicenter database. Significant FHR + ST events were evaluated post hoc in consensus by an expert panel. Results: Eighteen cases were not identified as in need of intervention and regarded as negative in the sensitivity analysis. In 12 cases ST changes occurred but the CTG was regarded as reassuring. Visual analysis of the FHR + ST tracings revealed the following specific FHR patterns: A. An instantaneous rise in beat-to- beat variations + ST event indicate an alarm reaction caused by instantaneously reduced cord vein blood flow and altered central hemodynamics evoking the heart protective Bezold-Jarisch reflex. B. A reduced beat-to-beat variation after a previous increase during 2nd stage of labor illustrating a situation where the fetal capacity is failing. C. Repeated decelerations in 2nd stage with recovery phase of < 2 minutes illustrating inadequate reoxygenation. Conclusions: These findings indicate FHR+ST analysis may be undertaken regardless of CTG classification system provided there is a more physiologically oriented approach to FHR assessment in connection with an ST event.

THE SIGNIFICANCE OF THE CHANGES IN THE CONTINUOUS FETAL HEART RATE IN THE FIRST STAGE OF LABOUR

Article

Apr 1972

Heart rate and blood pressure responses to umbilical cord compression in fetal lambs with special reference to the mechanism of variable deceleration

Article

Oct 1983
AM J OBSTET GYNECOL

We examined heart rate and blood pressure responses to umbilical cord compression in fetal lambs. Fetal heart rate (FHR) responses resembling variable deceleration occurred only after umbilical blood flow was reduced by at least 50%. These changes during partial cord occlusion varied directly with the reduced umbilical blood flow and were abolished by atropine; no significant changes in arterial pressure were observed. Complete cord occlusion caused severe bradycardia, a progressive increase in arterial pressure, and delayed recovery of FHR. With partial cord occlusion, the bradycardia was of chemoreceptor origin and was vagally mediated; with complete occlusion the bradycardia may have resulted from both chemoreceptor and baroreceptor stimulation. During prolonged partial cord occlusion, FHR decreased initially, then recovered to above control value; this occurred in the face of a significant acidosis. Thus, FHR responses to cord compression are dependent on the actual percentage of reduction in umbilical blood flow and on its duration.

Clinical fetal monitoring

Article

Sep 1975
AM J OBSTET GYNECOL

The clinical usage of intrapartum fetal monitoring has increased dramatically in the past few years. Understanding of the pathophysiologic significance of FHR patterns has been further elucidated, but quantitation and prediction on an individual basis at times present a practical clinical dilemma. Baseline FHR variability was evaluated in order to see if it provided additional commentary on fetal status. The presence of FHR variability appears to be a favorable commentary regarding both fetal and newborn status. A clinical method of appraising FHR is presented and the significance of FHR variability suggested.

Increased fetal heart rate variability in periventricular leukomalacia

Article

Aug 2015

This study used quantitative analysis to determine whether increased variability in fetal heart rate (FHR) is related to the risk of developing periventricular leukomalacia (PVL). We analyzed 124 FHR traces of neonates delivered preterm at 27-33weeks' gestation to 105 mothers. FHR traces 1-3h before delivery were translated into power-spectrum curves using a fast Fourier transformation. The total power (the area under the curve of 1-10 cycles per minute), segmental power of every cycle per minute, peak power, and frequency edges were calculated, and their relationship with the subsequent development of PVL was examined. Total power was significantly higher in the PVL group (n=9, median 1813, range 1064-2426) compared to the non-PVL group (n=114, median 1383, range 381-3324, p=0.029). Infants in the PVL group had greater segmental power in segments with 1-2, 2-3, and 9-10 cycles per minute, than those in the non-PVL group. Total power of ⩾1550 was significantly correlated with the subsequent development of PVL and premature rupture of membranes. Furthermore, the frequency of pregnancy-induced hypertension was significantly reduced in the fetuses with a total power of ⩾1550. Our study suggests that a fetus with increased FHR variability is at risk of developing PVL. This study provides additional evidence supporting the contribution of antenatal factors to the subsequent development of PVL. Copyright © 2015. Published by Elsevier B.V.

Saltatory and Sinusoidal Fetal Heart Rate (FHR) Patterns and significance of FHR ‘Overshoots’

Article

Jan 2013
Curr Wom Health Rev

Electronic fetal heart rate monitoring (EFM) in labour began its evolution in 1950s and became commercially available in late 1960s. EFM was introduced to identify those fetuses that were exposed to intrapartum hypoxia and were not able to tolerate ongoing hypoxic stress. Failure of compensatory mechanisms could lead to the development of respiratory and/or metabolic acidosis secondary to the intrapartum hypoxic insult, which if left undetected and treated, may have severe consequences. These include long-term implications such as learning difficulties, cerebral palsy and in some cases, increased risk of perinatal deaths. Use of EFM in high-risk labour has been associated with a significant reduction in fetal mortality rates and early onset neonatal seizures. The purpose of this article is to revisit the relatively uncommon findings of sinusoidal, overshoot and saltatory patterns in a cardiotocograph (CTG), their clinical implications and the approach to managing them in labour.

Fetal heart rate pattern in postasphyxated fetal lambs with brain damaged

Article

Jan 1997
AM J OBSTET GYNECOL

Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep

Article

Jul 1999
BJOG-INT J OBSTET GY

Objective To determine whether changes in fetal heart rate variation during repeated umbilical cord occlusions reflect evolving cardiovascular compromise in near term fetal sheep. Design Fetal heart rate variation, fetal mean arterial pressure, electroencephalogram (EEG) and acid-base status were measured during one minute umbilical cord occlusions, repeated either every five minutes (1 : 5 group) or every 2.5 minutes (1 : 2.5 group) for four hours or until mean arterial pressure fell below 20 mmHg for two successive occlusions. Sample Fourteen chronically instrumented fetal sheep, mean gestation 126.3 (2.6) days. Results Cord occlusion caused variable decelerations with initial sustained hypertension. In the 1:5 occlusion group mean arterial pressure remained elevated throughout, with little change in acid-base status (pH = 7.34 (0.07), base deficit = 1.3 (3.9) after 4 hours) and no significant change in fetal heart rate variation. In contrast, in the 1:2.5 group from the third occlusion there was progressive hypotension during occlusions, severe progressive metabolic acidaemia (pH 6.92 (0.1), base deficit 17.0 mmol/L (4.7) after the last occlusion) and marked EEG suppression (P < 0.01). Fetal heart rate variation increased with the onset of occlusions (P < 0.05) and then progressively fell with continued occlusions. During the last 30 minutes of occlusions, fetal heart rate variation was severely suppressed in four, but increased in two fetuses, while all six fetuses developed overshoot-instability of fetal heart rate and mean arterial pressure following each occlusion. Conclusions Acute progressive asphyxia was typically associated with an immediate, transient increase in fetal heart rate variation. Subsequently variation became suppressed in only two-thirds of fetuses during terminal acidaemia and hypotension. Fetal heart rate overshoot-instability may be a useful marker of fetal decompensation following variable decelerations.

The effect of carotid sinus denervation on fetal heart rate variation in normoxia, hypoxia and post‐hypoxia in fetal sheep

Article

Apr 1997
BJOG-INT J OBSTET GY

Objective: To investigate whether carotid sinus nerve reflexes are linked to the increase in heart rate variation in acute (one hour) hypoxia in late gestation fetal sheep Design: Comparison of short term variation between intact and carotid sinus denervated fetuses in normoxia, hypoxia and post-hypoxia. Subjects: Sixteen chronically catheterised pregnant sheep in late gestation. Results: There was no significant difference in short term variation between intact and denervated fetuses in normoxia. In intact fetuses short term variation increased significantly in hypoxia. In denervated fetuses it tended to increase in hypoxia, but this was not statistically significant. During the post-hypoxia period, short term variation increased significantly in denervated fetuses, although at this time it was decreasing in intact fetuses. When the decrease in pH was small intact fetuses showed a significantly greater increase in short term variation than denervated fetuses in hypoxia. In contrast, short term variation increased similarly in both groups when the pH decrease was greater (> 0.03 in early hypoxia and > 0.05 in late hypoxia). Conclusions: Carotid sinus nerve reflexes have an important influence on heart rate variation in hypoxia and post-hypoxia. It appears that other mechanisms (e.g. a rise in circulating catecholamines) are linked to an increase in heart rate variation when mild acidemia occurs in hypoxia.

Clinical fetal monitoring. VII. The evaluation and significance of intrapartum baseline FHR variability

Article

Oct 1975
AM J OBSTET GYNECOL

The clinical usage of intrapartum fetal monitoring has increased dramatically in the past few years. Understanding of the pathophysiologic significance of FHR patterns has been further elucidated, but quantitation and prediction on an individual basis at times present a practical clinical dilemma. Baseline FHR variability was evaluated in order to see if it provided additional commentary on fetal status. The presence of FHR variability appears to be a favorable commentary regarding both fetal and newborn status. A clinical method of apprasing FHR is presented and the significance of FHR variability suggested.

Clinical significance of fetal heart rate patterns during labor. I. Baseline patterns

Article

Jul 1976
AM J OBSTET GYNECOL

Luis A. Cibils

From a population of 2,774 high-risk patients monitored during labor, 1,304 single pregnancies in cephalic presentation and with direct monitoring for at least 1 hour before completion or cesarean-section were studied. The maternal and fetal clinical data and the tracings were hand reviewed, coded, and programmed for computer analysis. In the record were studied baseline, its changes (tachycardia, fixed, saltatory), the accelerations, and the decelerations (early, variable, late). Fifty-four per cent had some type of FHR deceleration. Accelerations were recorded in over 12 per cent of all cases and were associated with cord problems in 41 per cent. Subgrouping the patients by age of gestation (less than or equal to 36 weeks, 37 to 41 weeks, and greater than or equal to 42 weeks) revealed a 10 per cent prolonged gestation rate and only 6.8 per cent premature; these had a lower 5 minute Apgar score. Fetal weight and age were positively correlated with Apgar score. Baseline changes were much frequent among pre- and postmature infants, particularly tachycardia in the latter (40 per cent). The premature infants had a 25 per cent incidence of fetal distress and the postmature infants had 20 per cent. Neonatal morbidity and mortality rates were very high among premature infants and a mortality rate of 2.3 per cent was found among postmature infants. Saltatory pattern and particularly fixed baseline seem characteristic of prolonged gestation and placental insufficiency. With tachycardia, they constitute subtle symptoms of fetal distress.

Saltatory fetal heart rate pattern

Article

Apr 1992
J PERINATOL

A retrospective descriptive study reviewed 433 consecutive intrapartum fetal heart tracings. The saltatory fetal heart rate pattern was defined as fetal heart amplitude changes of greater than 25 beats per minute with an oscillatory frequency of greater than 6 per minute for a minimum duration of 1 minute. Data were analyzed for each mother-infant pair over the time of labor and birth. The saltatory pattern was demonstrated in 10 of the 433 tracings reviewed for an overall incidence of 2.3%. All 10 fetuses demonstrating the saltatory pattern were term (38 to 42 weeks' gestation). None of the 147 preterm fetuses demonstrated the saltatory pattern (P less than .02). In 6 patients the saltatory pattern was observed after parenteral ephedrine administration, in 3 patients with uterine hyperstimulation, and in 1 patient during cervical examination. When the saltatory pattern was seen with ephedrine administration, it was present only at total doses of greater than or equal to 30 mg (P less than .001). In all patients the saltatory pattern occurred during active phase or second stage of labor. Short-term and long-term variability recorded by the fetal-scalp electrode were present both before and after the episode of saltatory pattern. At birth, all 10 infants were vigorous, with Apgar scores of 8/9 or 9/9. In the absence of abnormal periodic fetal heart rate changes and with the presence of short-term and long-term variability, the saltatory fetal heart rate pattern appears benign.

Fetal monitoring casebook. The saltatory fetal heart rate pattern

Article

Jan 1992
J PERINATOL

The significance of the changes in the continuous FHR in the first stage of labour

Article

Nov 1971
J Obstet Gynaecol Br Commonwealth

A comparison between data derived from changes in fetal heart rate and p H of fetal blood in 279 high-risk patients is described. The incidence of fetal acidosis was low when the continuous record of FHR showed good beat-to-beat variation in rhythm and no slowing during uterine contractions. The incidence of fetal acidosis accompanying fetal tachycardia or bradycardia was low if the rate remained unaltered during contractions. Decelerations of fetal heart rate accompanied by baseline tachycardia and/or loss of beat-to-beat variation were the changes most commonly associated with fetal acidosis and hence, by inference, with fetal asphyxia. Deep and/or delayed decelerations were also suggestive of fetal asphyxia. Late decelerations, although at first sight innocuous, were frequently found to be a sign of severe fetal asphyxia.

Heart Rate and Blood Pressure Responses to Umbilical Cord Compression in Fetal Lambs with Special Reference to the Mechanism of Variable Deceleration

Article

Nov 1983
AM J OBSTET GYNECOL

The effect of fetal heart rate on cardiovascular function during hypoxemia

Article

Jan 1981
AM J OBSTET GYNECOL

The effect of heart rate changes on cardiovascular function during hypoxemia was studied in lamb fetuses. In chronic preparations, we determined fetal heart rate, descending aortic blood flow (by electromagnetic flowmeter), PO2, PCO2, and pH and calculated fetal cardiac output (CO) and organ blood flows (with the use of 15 mu nuclide-labeled microspheres). Observations were made during control and hypoxemic states either alone or in the presence of parasympathetic blockade by atropine. Fetuses exposed to moderate hypoxemia (ewe breathing 10% oxygen) developed a significant bradycardia which was prevented by atropine pretreatment; no significant change in CO occurred in either case. Fetuses exposed to severe hypoxemia (8% oxygen) developed bradycardia and a significant decrease in CO; atropine pretreatment prevented the bradycardia but failed to prevent the decrease in CO. Atropine administered to the already severely hypoxemic fetus increased the heart rate but did not restore the depressed CO. The redistribution of blood flow from low-priority (e.g., viscera) to high-priority (e.g., myocardium) tissues correlated with the degree of hypoxemia. Myocardial blood flow was greater during hypoxemia when bradycardia was prevented by atropine than during hypoxemia alone; otherwise, blood flow distribution in response to hypoxemia was unaffected by atropine blockade.

The autonomic nervous system and fetal heart rate variability

Article

Jul 1983
AM J OBSTET GYNECOL

Although it is often assumed that fetal heart rate variability reflects simple "push-pull" interactions between the parasympathetic and beta-sympathetic limbs of the autonomic nervous system, there has been little direct experimental evidence to support this view. We used autonomic blocking agents to investigate heart rate variability in chronically catheterized fetal lambs, and an on-line computer to make measurements of heart rate and of the higher and lower frequency components of its variability. beta-sympathetic blockade alone had no effect on variability. Parasympathetic blockade alone reduced it, but did not abolish it. Even after double blockade, some 35% to 40% of variability remained, thus implying that there is a major nonneural component to heart rate variability. There was evidence that the fetus, unlike the adult, is subject to a resting cardioacceleratory drive.

Influence of maternal heart rate and gross fetal body movements on the daily pattern of fetal heart rate near term

Article

Dec 1982
AM J OBSTET GYNECOL

Continuous measurements of fetal heart rate (FHR), gross fetal body movements, fetal breathing movements, and maternal heart rate (MHR) were made for 24-hour observation intervals in 11 pregnant women at 38 to 40 weeks. There was a significant positive correlation between each mother's daily mean MHR and her fetus' daily mean FHR. There was a trough in mean hourly FHR between 0200 and 0600 hours and a trough in mean hourly MHR between 2400 and 0700 hours. Mean hourly FHR both during and between times of gross fetal body movements was significantly correlated to mean hourly MHR. At term, the mean FHR is strongly influenced by the mean MHR and the presence or absence of gross fetal body movements.

Increased fetal heart rate variability with acute hypoxia in chronically instrumented sheep

Article

Aug 1980
EUR J OBSTET GYN R B

Fetal heart rate (FHR) and oxygen consumption were determined in 45 studies in 20 chronically instrumented, normoxic sheep. FHR variability was measured by a template device to determine amplitude range, and oscillatory frequency was manually counted over 5-min periods. During 26 min of isocapnic hypoxia, fetal O2 consumption decreased 39% and FHR decreased 18%, and FHR variability increased, the changes being maintained over the treatment period. It is suggested that the maintenance of FHR variability during this profound hypoxia denotes adequate cardiorespiratory compensatory mechanisms during the short period; prolongation of the hypoxia would probably result in fetal cerebral or myocardial decompensation, and disappearance of FHR variability. The increased variability may be due to increased alpha-adrenergic activity.

Changes in fetal heart rate associated with fetal breathing and fetal movement

Article

Jan 1981
Br J Obstet Gynaecol

Thirty-eight recordings of fetal heart rate and fetal activity were made from 21 normal patients between 36 and 41 weeks gestation. Each recording lasted for an average of 39 minutes. The heart rate was measured from beat to beat using the R-wave of the fetal electrocardiogram as the indicator of each heart-beat. Fetal breathing movements and fetal body movements were detected using either A-mode or B-mode ultrasound systems. The relation of fetal breathing and fetal movement to the fetal heart rate was studied both by cardiotachography and computer analysis of the R--R intervals. Fetal body movements (kicking and rolling) were usually associated with a brief tachycardia, the latter typically occurring every two to three minutes. In 14 recordings, the periods of fetal activity were interrupted by periods of fetal rest with an average duration of 12.5 minutes. Fetal breathing was seen in 26 of the 34 recordings analysed and occurred principally during the periods of fetal activity. Fetal breathing was associated with a significant increase in heart rate variation measured as the standard deviation of the R--R intervals and the mean absolute R--R interval difference. Sometimes a pattern of respiratory sinus arrhythmia was seen.

Fetal heart rate patterns associated with periventricular leukomalacia

Article

Jan 1997

Our purpose was to assess the applicability of fetal heart rate (FHR) monitoring to detect fetuses at risk of developing periventricular leukomalacia (PVL). FHR tracings obtained for babies delivered under 33 weeks' gestation and with a birth weight under 2000 g were assessed for baseline heart rate, variability, deceleration and "flip flap' (an oscillatory tracing pattern). PVL developed in 19 of the 103 infants studied. All of these infants were among the fetuses who exhibited average and increased variability. In addition, PVL was detected in 10 (47.6%) of the 21 flip flap positive fetuses, and in 9 (11.0%) of the 82 flip flap negative fetuses. The incidence of PVL was significantly higher in the flip flap positive fetuses (P < 0.005). The possibility that an unstable intrauterine environment, reflected by a flip flap pattern, is related to the subsequent development of PVL is indicated.

Fetal heart rate patterns in growth-restricted fetal sheep induced by chronic fetal placental embolization

Article

Mar 1997
AM J OBSTET GYNECOL

Our purpose was to test the hypothesis that chronic placental insufficiency and intrauterine growth restriction in fetal sheep causes a decrease in the number of fetal heart rate accelerations and fetal heart rate variability. Chronically catheterized fetal sheep were embolized (n = 6) daily with 15 to 50 microns latex microspheres for 21 days between 0.74 and 0.88 of gestation into the abdominal aorta, until fetal arterial oxygen content was decreased by 40% to 50% of the preembolization value. Control animals (n = 6) received saline solution only. Signals from chest electrodes were analyzed on-line with the Sonicaid System 8000 in 2-hour epochs every 6 hours starting at 8 AM over the first 48 hours of hypoxemia and for 2 hours between 8 and 10 AM every other day from day 3 to day 21 of hypoxemia. Umbilical artery Doppler-derived resistance index and fetal plasma catecholamine concentrations were also measured. Embolized fetuses had asymmetric intrauterine growth restriction and became chronically hypoxemic (p < 0.001) with a progressive increase in the umbilical artery resistance index (p < 0.001). During the first 48 hours of hypoxemia the number of accelerations and decelerations and both short- and long-term fetal heart rate variability increased initially, followed by a return to control levels by 20 hours after the onset of embolization. After 21 days of hypoxemia the number of accelerations was significantly reduced by 30% compared with controls (p < 0.05). Both short- and long-term fetal heart rate variability in control fetuses gradually increased with advancing gestational age (p < 0.001 and p < 0.01, respectively), whereas in embolized fetuses the fetal heart rate variability remained unchanged and was 20% lower than that of controls on day 21 (both p < 0.01). Intrauterine growth restriction and long-term hypoxemia in fetal sheep are associated with a decrease in short- and long-term fetal heart rate variability, possibly because of a delay in the normal maturational changes of the autonomic control of fetal heart rate.

Fetal heart rate patterns in post asphyxiated fetal lambs with brain

Article

Dec 1998
AM J OBSTET GYNECOL

We previously showed that in asphyxiated fetal lambs the duration of hypotension correlated well with the severity of histologic damage to the brain, whereas the duration of bradycardia did not. This study compares fetal heart rate patterns with the degree of histologic damage to the brain. Twelve chronically instrumented near-term fetal lambs were subjected to asphyxia by umbilical cord occlusion until fetal arterial pH was <6. 9 and base excess was <-20 mEq/L. An additional 4 fetuses served as sham-asphyxia controls. Fetal heart rate (from electrocardiogram), arterial blood pressure, fetal breathing movements, and electrocorticogram were continuously monitored before, during, and for 72 hours after asphyxia. Fetal brain histologic features were categorized as mild (group 1, n = 5), moderate (group 2, n = 4), and severe (group 3, n = 3). Long-term fetal heart rate variability expressed as amplitude range was assessed visually every 5 minutes from 30 minutes before asphyxia until 2 hours of recovery and at 6, 12, 24, 48, and 72 hours of recovery. Long-term fetal heart rate variability amplitude decreased from 32 +/- 17 beats/min (mean +/- SEM) preocclusion to 4 +/- 13 beats/min at the end of occlusion (P <.001) without significant differences among the 3 groups. During 10 to 45 minutes of recovery, the long-term variability of group 1 was significantly greater than that of groups 2 and 3. At 24 to 72 hours of recovery, the long-term variability of groups 1 and 2 was significantly higher than that of group 3, which was almost 0. The "checkmark" and sinusoidal fetal heart rate patterns were observed during the recovery period in groups 2 and 3. Decreased long-term fetal heart rate variability and the "checkmark" and sinusoidal fetal heart rate patterns were indicators of the severity of asphyxial histologic damage in the fetal brain.

Fetal seizures causing increased heart rate variability during terminal fetal hypoxia

Article

Oct 1999
AM J OBSTET GYNECOL

Fetal seizures together with both abnormal breathing movements and fluctuations in fetal blood pressure and heart rate resulting in increased fetal heart rate variability have been observed in brain-damaged fetal sheep shortly after an asphyxial insult. We report a clinical example of convulsions and increased heart rate variability during terminal fetal hypoxia.

Fetal heart rate variability and brain stem injury after asphyxia in preterm fetal sheep

Article

Nov 2004

This study was undertaken to determine the mechanisms mediating changes in fetal heart rate variability (FHRV) during and after exposure to asphyxia in the premature fetus. Preterm fetal sheep at 0.6 of gestation (91 +/- 1 days, term is 147 days) were exposed to either sham occlusion (n = 10) or to complete umbilical cord occlusion for either 20 (n = 7) or 30 min (n = 10). Cord occlusion led to a transient increase in FHRV with abrupt body movements that resolved after 5 min. In the 30 min group there was a marked increase in FHRV in the final 10 min of occlusion related to abnormal atrial activity. After reperfusion, FHRV in both study groups was initially suppressed and progressively increased to baseline levels over the first 4 h of recovery. In the 20 min group this improvement was associated with return of normal EEG activity and movements. In contrast, in the 30 min group the EEG was abnormal with epileptiform activity superimposed on a suppressed background, which was associated with abnormal fetal movements. As the epileptiform activity resolved, FHRV fell and became suppressed for the remainder of the study. Histological assessment after 72 h demonstrated severe brain stem injury in the 30 min group but not in the 20 min group. In conclusion, during early recovery from asphyxia, epileptiform activity and associated abnormal fetal movements related to evolving neural injury can cause a confounding transient increase in FHRV, which mimics the normal pattern of recovery. However, chronic suppression of FHRV was a strong predictor of severe brain stem injury.

The intrapartum deceleration in center stage: a physiologic approach to the interpretation of fetal heart rate changes in labor

Article

Oct 2007

One of the most distinctive features of fetal heart rate recordings in labor is the deceleration. In clinical practice, there has been much confusion about the types of decelerations and their significance. In the present review, we examined uteroplacental perfusion in labor, describe the pathophysiologic condition of decelerations, and explain some of the reasons behind the confusion about the terminology. We summarize recent studies that systematically have dissected the features of variable decelerations that may help to identify developing fetal compromise, such as the slope of the deceleration, overshoot, and variability changes. Although no pattern of repeated deep decelerations is necessarily benign, fetuses with normal placental reserve can compensate fully, even for frequent deep but brief decelerations, for surprisingly prolonged intervals before the development of profound acidosis and hypotension. This tolerance reflects the remarkable ability of the fetus to adapt to repeated hypoxia. We propose that, rather than focus on descriptive labels, clinicians should be trained to understand the physiologic mechanisms of fetal heart rate decelerations and the patterns of fetal heart rate change that indicate progressive loss of fetal compensation.

Does the saltatory pattern on cardiotocograph (CTG) trace really exist? The ZigZag pattern as an alternative definition and its correlation with perinatal outcomes

Abstract

No full-text available

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