A sustained decrease in the systolic/diastolic ratio may be a sign of severe adverse events in the umbilical cord: a report of eight cases.

A high systolic/diastolic (S/D) ratio of umbilical cord blood is a manifestation of intrauterine hypoxia. However, the clinical significance of a persistently decreased S/D ratio of umbilical cord blood has not been reported. We report eight cases of a persistently decreased S/D ratio of umbilical cord blood, with two cases of umbilical thrombus, five cases of excessive torsion, and one case of a true cord knot. Fetuses with a persistently decreased S/D ratio of umbilical cord blood may be at risk, and it may be an important indication of umbilical cord lesions.

Machine learning on cardiotocography data to classify fetal outcomes: A scoping review.

INTRODUCTION: Uterine contractions during labour constrict maternal blood flow and oxygen delivery to the developing baby, causing transient hypoxia. While most babies are physiologically adapted to withstand such intrapartum hypoxia, those exposed to severe hypoxia or with poor physiological reserves may experience neurological injury or death during labour. Cardiotocography (CTG) monitoring was developed to identify babies at risk of hypoxia by detecting changes in fetal heart rate (FHR) patterns. CTG monitoring is in widespread use in intrapartum care for the detection of fetal hypoxia, but the clinical utility is limited by a relatively poor positive predictive value (PPV) of an abnormal CTG and significant inter and intra observer variability in CTG interpretation. Clinical risk and human factors may impact the quality of CTG interpretation. Misclassification of CTG traces may lead to both under-treatment (with the risk of fetal injury or death) or over-treatment (which may include unnecessary operative interventions that put both mother and baby at risk of complications). Machine learning (ML) has been applied to this problem since early 2000 and has shown potential to predict fetal hypoxia more accurately than visual interpretation of CTG alone. To consider how these tools might be translated for clinical practice, we conducted a review of ML techniques already applied to CTG classification and identified research gaps requiring investigation in order to progress towards clinical implementation. MATERIALS AND METHOD: We used identified keywords to search databases for relevant publications on PubMed, EMBASE and IEEE Xplore. We used Preferred Reporting Items for Systematic Review and Meta-Analysis for Scoping Reviews (PRISMA-ScR). Title, abstract and full text were screened according to the inclusion criteria. RESULTS: We included 36 studies that used signal processing and ML techniques to classify CTG. Most studies used an open-access CTG database and predominantly used fetal metabolic acidosis as the benchmark for hypoxia with varying pH levels. Various methods were used to process and extract CTG signals and several ML algorithms were used to classify CTG. We identified significant concerns over the practicality of using varying pH levels as the CTG classification benchmark. Furthermore, studies needed to be more generalised as most used the same database with a low number of subjects for an ML study. CONCLUSION: ML studies demonstrate potential in predicting fetal hypoxia from CTG. However, more diverse datasets, standardisation of hypoxia benchmarks and enhancement of algorithms and features are needed for future clinical implementation.

Large-scale analysis of interobserver agreement and reliability in cardiotocography interpretation during labor using an online tool.

BACKGROUND: While the effectiveness of cardiotocography in reducing neonatal morbidity is still debated, it remains the primary method for assessing fetal well-being during labor. Evaluating how accurately professionals interpret cardiotocography signals is essential for its effective use. The objective was to evaluate the accuracy of fetal hypoxia prediction by practitioners through the interpretation of cardiotocography signals and clinical variables during labor. MATERIAL AND METHODS: We conducted a cross-sectional online survey, involving 120 obstetric healthcare providers from several countries. One hundred cases, including fifty cases of fetal hypoxia, were randomly assigned to participants who were invited to predict the fetal outcome (binary criterion of pH with a threshold of 7.15) based on the cardiotocography signals and clinical variables. After describing the participants, we calculated (with a 95% confidence interval) the success rate, sensitivity and specificity to predict the fetal outcome for the whole population and according to pH ranges, professional groups and number of years of experience. Interobserver agreement and reliability were evaluated using the proportion of agreement and Cohen's kappa respectively. RESULTS: The overall ability to predict a pH level below 7.15 yielded a success rate of 0.58 (95% CI 0.56-0.60), a sensitivity of 0.58 (95% CI 0.56-0.60) and a specificity of 0.63 (95% CI 0.61-0.65). No significant difference in the success rates was observed with respect to profession and number of years of experience. The success rate was higher for the cases with a pH level below 7.05 (0.69) and above 7.20 (0.66) compared to those falling between 7.05 and 7.20 (0.48). The proportion of agreement between participants was good (0.82), with an overall kappa coefficient indicating substantial reliability (0.63). CONCLUSIONS: The use of an online tool enabled us to collect a large amount of data to analyze how practitioners interpret cardiotocography data during labor. Despite a good level of agreement and reliability among practitioners, the overall accuracy is poor, particularly for cases with a neonatal pH between 7.05 and 7.20. Factors such as profession and experience level do not present notable impact on the accuracy of the annotations. The implementation and use of a computerized cardiotocography analysis software has the potential to enhance the accuracy to detect fetal hypoxia, especially for ambiguous cardiotocography tracings.

EUROPEAN ASSOCIATION OF PERINATAL MEDICINE (EAPM) Position statement: Use of appropriate terminology for situations related to inadequate fetal oxygenation in labor.

In high-resource countries, adverse perinatal outcomes are currently rare in term, non-malformed fetuses, undergoing labor, but they remain a leading cause of medico-legal dispute. Precise terminology is important to describe situations related to inadequate fetal oxygenation in labor, to ensure appropriate communication between healthcare professionals and adequate transmission of information to parents. This position statement provides consensus definitions from European perinatologists and midwives regarding the most appropriate terminology to describe situations related to inadequate fetal oxygenation in labor: suspected fetal hypoxia, severe newborn acidemia, newborn metabolic acidosis, and hypoxic-ischemic encephalopathy. It also identifies terms that are imprecise or nonspecific to this situation, and should therefore be avoided by healthcare professionals: fetal well-being, fetal stress, fetal distress, non-reassuring fetal state, and birth asphyxia.

Fetal monitoring technologies for the detection of intrapartum hypoxia - challenges and opportunities.

Intrapartum fetal hypoxia is related to long-term morbidity and mortality of the fetus and the mother. Fetal surveillance is extremely important to minimize the adverse outcomes arising from fetal hypoxia during labour. Several methods have been used in current clinical practice to monitor fetal well-being. For instance, biophysical technologies including cardiotocography, ST-analysis adjunct to cardiotocography, and Doppler ultrasound are used for intrapartum fetal monitoring. However, these technologies result in a high false-positive rate and increased obstetric interventions during labour. Alternatively, biochemical-based technologies including fetal scalp blood sampling and fetal pulse oximetry are used to identify metabolic acidosis and oxygen deprivation resulting from fetal hypoxia. These technologies neither improve clinical outcomes nor reduce unnecessary interventions during labour. Also, there is a need to link the physiological changes during fetal hypoxia to fetal monitoring technologies. The objective of this article is to assess the clinical background of fetal hypoxia and to review existing monitoring technologies for the detection and monitoring of fetal hypoxia. A comprehensive review has been made to predict fetal hypoxia using computational and machine-learning algorithms. The detection of more specific biomarkers or new sensing technologies is also reviewed which may help in the enhancement of the reliability of continuous fetal monitoring and may result in the accurate detection of intrapartum fetal hypoxia.

Machine Learning to Classify Cardiotocography for Fetal Hypoxia Detection.

Fetal hypoxia can cause damaging consequences on babies' such as stillbirth and cerebral palsy. Cardiotocography (CTG) has been used to detect intrapartum fetal hypoxia during labor. It is a non-invasive machine that measures the fetal heart rate and uterine contractions. Visual CTG suffers inconsistencies in interpretations among clinicians that can delay interventions. Machine learning (ML) showed potential in classifying abnormal CTG, allowing automatic interpretation. In the absence of a gold standard, researchers used various surrogate biomarkers to classify CTG, where some were clinically irrelevant. We proposed using Apgar scores as the surrogate benchmark of babies' ability to recover from birth. Apgar scores measure newborns' ability to recover from active uterine contraction, which measures appearance, pulse, grimace, activity and respiration. The higher the Apgar score, the healthier the baby is.We employ signal processing methods to pre-process and extract validated features of 552 raw CTG. We also included CTG-specific characteristics as outlined in the NICE guidelines. We employed ML techniques using 22 features and measured performances between ML classifiers. While we found that ML can distinguish CTG with low Apgar scores, results for the lowest Apgar scores, which are rare in the dataset we used, would benefit from more CTG data for better performance. We need an external dataset to validate our model for generalizability to ensure that it does not overfit a specific population.Clinical Relevance- This study demonstrated the potential of using a clinically relevant benchmark for classifying CTG to allow automatic early detection of hypoxia to reduce decision-making time in maternity units.

Clinical practice guidelines for intrapartum cardiotocography interpretation: A systematic review.

BACKGROUND: Clinical practice guidelines on intrapartum cardiotocography (CTG) interpretation provide structured tools to detect fetal hypoxia. Despite frequent use of different guidelines, little is known about their comparable consistency. We sought to appraise guidelines relevant to intrapartum CTG interpretation and summarise consensus and non-consensus recommendations. AIMS: To compare existing intrapartum CTG interpretation guidelines. MATERIALS AND METHODS: We searched PubMed, CINAHL, Cochrane, Embase, guideline databases and websites of guideline development institutions using terms 'cardiotocography', 'electronic fetal/foetal monitoring', and 'guideline' or equivalent term. The search was restricted to English-language articles published between January 1980 and January 2023 and excluded animal studies. The initial search yielded 2128 articles with 1253 unique citations. Guidelines were included if they: used English as the reporting language; included CTG interpretation criteria or guidelines as a primary objective; were published or updated since 1980; and were the most recently updated publications when multiple versions were identified. RESULTS: Nineteen studies were considered for full review, and 13 met inclusion criteria. Two reviewers independently assessed guideline quality using the AGREE II instrument, and synthesised consensus and non-consensus recommendations using the content analysis approach. Most guidelines employed a three-tier interpretation framework. There were significant differences between the guidelines for relative importance of key CTG features such as accelerations, decelerations and variability, with respect to the outcome of fetal hypoxia. CONCLUSIONS: There are significant differences between key intrapartum CTG interpretation guidelines currently being used. Greater consistency is needed across CTG interpretation guidelines to improve the quality of data, clinical governance, monitoring of outcomes, and to support future developments.

A second look at intrapartum fetal surveillance and future directions.

Intrapartum fetal surveillance aims to predict significant fetal hypoxia and institute timely intervention to avoid fetal injury, and do so without unnecessary operative delivery of fetuses at no risk of intrapartum hypoxia. However, the configuration and application of current clinical guidelines inadvertently undermine these aims because of persistent failure to incorporate increased understanding of fetal cardiovascular physiology and adaptations to oxygen deprivation, advances in signal acquisition/processing, and related technologies. Consequently, the field on intrapartum fetal surveillance is stuck in rudimentary counts of the fetal R-R intervals and visual assessment of very common, but nonspecific fetal heart decelerations and fetal heart rate variability. The present authors argue that the time has come to move away from classifications of static morphological appearances of FHR decelerations, which do not assist the thinking clinician in understanding how the fetus defends itself and compensates for intrapartum hypoxic ischaemic insults or the patterns that suggest progressive loss of compensation. We also reappraise some of the controversial aspects of intrapartum fetal surveillance in modern obstetric practice, the current state of flux in training and certification, and contemplate the future of the field particularly in the context of the emerging role of artificial intelligence.

Computerized cardiotocography analysis during labor - A state-of-the-art review.

Cardiotocography is defined as the recording of fetal heart rate and uterine contractions and is widely used during labor as a screening tool to determine fetal wellbeing. The visual interpretation of the cardiotocography signals by the practitioners, following common guidelines, is subject to a high interobserver variability, and the efficiency of cardiotocography monitoring is still debated. Since the 1990s, researchers and practitioners work on designing reliable computer-aided systems to assist practitioners in cardiotocography interpretation during labor. Several systems are integrated in the monitoring devices, mostly based on the guidelines, but they have not clearly demonstrated yet their usefulness. In the last decade, the availability of large clinical databases as well as the emergence of machine learning and deep learning methods in healthcare has led to a surge of studies applying those methods to cardiotocography signals analysis. The state-of-the-art systems perform well to detect fetal hypoxia when evaluated on retrospective cohorts, but several challenges remain to be tackled before they can be used in clinical practice. First, the development and sharing of large, open and anonymized multicentric databases of perinatal and cardiotocography data during labor is required to build more accurate systems. Also, the systems must produce interpretable indicators along with the prediction of the risk of fetal hypoxia in order to be appropriated and trusted by practitioners. Finally, common standards should be built and agreed on to evaluate and compare those systems on retrospective cohorts and to validate their use in clinical practice.

Cerebral Palsy and Criteria Implicating Intrapartum Hypoxia in Neonatal Encephalopathy - An Obstetric Perspective for the South African Setting.

The science surrounding cerebral palsy indicates  that it is a complex medical condition with multiple contributing variables and factors, and causal pathways are often extremely difficult to delineate. The pathophysiological processes are often juxtaposed on antenatal factors, genetics, toxins, fetal priming, failure of neuroscientific autoregulatory mechanisms, abnormal biochemistry and abnormal metabolic pathways. Placing this primed compromised compensated brain through the stresses of an intrapartum process could be the final straw in the pathway  to brain injury and later CP.  It is thus simplistic to base causation of cerebral palsy on only an intrapartum perspective with radiological 'confirmation', as is often the practice in medicolegal cases in South African courts. The present modalities (MRI and CTG when available) that retrospectively attempt to determine causation in courts are inadequate when used in isolation. Unless a holistic scientific review of the case including all contributing clinical factors (antepartum, intrapartum and neonatal), fetal heart rate monitoring, neonatal MRI if possible (and preferred) or late MRI, and histology (placental histology if performed) are taken into account, success for plaintiff or defendant currently in a court of law will depend on eloquent legal argument rather than true scientific causality. The 10 criteria set out in this document to implicate acute intrapartum hypoxia in hypoxic ischaemic encephalopathy/neonatal encephalopathy serve as a guideline in the medicolegal setting.

CD15 immunostaining improves placental diagnosis of fetal hypoxia.

INTRODUCTION: Fetal hypoxic events with unclear predictive value are a common indication for placenta examination. We evaluated whether the use of CD15 immunostaining can improve the assessment of severity and duration of fetal hypoxia. METHODS: We compared placentas (37-42 gestational weeks) from stillborns/newborns with birth asphyxia (BA) and non-hypoxic newborns. Placental findings were studied in following groups: (1) acute BA (n = 11) due to placental abruption, (2) non-acute BA (n = 121) due to non-acute conditions, (3) non-BA (n = 46) in pregnancies with preeclampsia and gestational diabetes, and (4) controls (n = 30). RESULTS: A high expression of CD15 in feto-placental resistance vessels (FRVs) was present in non-acute BA (95.9%), but absent in acute BA, non-BA and controls (p < 0.0001). Furthermore, we found no causal relationship of high expression of CD15 in FRVs to coexisting placental conditions, including severity and mechanisms/patterns of placental injury, fetal erythroblastosis, and maternal conditions. According to a multivariate analysis, only a high expression of CD15 in FRVs was independently associated with severe non-acute fetal hypoxia ([OR] = 15.52; 95% [CI] = 5.92-40.67). DISCUSSION: We have defined a characteristic pattern of CD15 expression in FRVs that allows to interpret various clinical/placental conditions with respect to fetal hypoxia, with an improved predictability compared to conventional analyses. This approach represents a novel diagnostic strategy for placenta examination, which could indirectly assess severity and duration of intrauterine hypoxia in a heterogeneous population of newborns.

Maternal Oxygen Supplementation Compared With Room Air for Intrauterine Resuscitation: A Systematic Review and Meta-analysis.

Importance: Supplemental oxygen is commonly administered to pregnant women at the time of delivery to prevent fetal hypoxia and acidemia. There is mixed evidence on the utility of this practice. Objective: To compare the association of peripartum maternal oxygen administration with room air on umbilical artery (UA) gas measures and neonatal outcomes. Data Sources: Ovid MEDLINE, Embase, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials were searched from February 18 to April 3, 2020. Search terms included labor or obstetric delivery and oxygen therapy and fetal blood or blood gas or acid-base imbalance. Study Selection: Studies were included if they were randomized clinical trials comparing oxygen with room air at the time of scheduled cesarean delivery or labor in patients with singleton, nonanomalous pregnancies. Studies that did not collect paired umbilical cord gas samples or did not report either UA pH or UA Pao2 results were excluded. Data Extraction and Synthesis: Data were extracted by 2 independent reviewers. The analysis was stratified by the presence or absence of labor at the time of randomization. Data were pooled using random-effects models. Main Outcomes and Measures: The primary outcome for this review was UA pH. Secondary outcomes included UA pH less than 7.2, UA Pao2, UA base excess, 1- and 5-minute Apgar scores, and neonatal intensive care unit admission. Results: The meta-analysis included 16 randomized clinical trials (n = 1078 oxygen group and n = 974 room air group). There was significant heterogeneity among the studies (I2 = 49.88%; P = .03). Overall, oxygen administration was associated with no significant difference in UA pH (weighted mean difference, 0.00; 95% CI, -0.01 to 0.01). Oxygen use was associated with an increase in UA Pao2 (weighted mean difference, 2.57 mm Hg; 95% CI, 0.80-4.34 mm Hg) but no significant difference in UA base excess, UA pH less than 7.2, Apgar scores, or neonatal intensive care unit admissions. Umbilical artery pH values remained similar between groups after accounting for the risk of bias, type of oxygen delivery device, and fraction of inspired oxygen. After stratifying by the presence or absence of labor, oxygen administration in women undergoing scheduled cesarean delivery was associated with increased UA Pao2 (weighted mean difference, 2.12 mm Hg; 95% CI, 0.09-4.15 mm Hg) and a reduction in the incidence of UA pH less than 7.2 (relative risk, 0.63; 95% CI, 0.43-0.90), but these changes were not noted among those in labor (Pao2: weighted mean difference, 3.60 mm Hg; 95% CI, -0.30 to 7.49 mm Hg; UA pH<7.2: relative risk, 1.34; 95% CI, 0.58-3.11). Conclusions and Relevance: This systematic review and meta-analysis suggests that studies to date showed no association between maternal oxygen and a clinically relevant improvement in UA pH or other neonatal outcomes.

Intrapartum zigzag pattern of fetal heart rate is an early sign of fetal hypoxia: A large obstetric retrospective cohort study.

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 over 1 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, the 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%. No case of saltatory pattern (baseline amplitude changes of >25 bpm with a duration of >30 minutes) was observed. The presence of the ZigZag pattern or late decelerations, or both, was associated with cord blood acidemia (odds ratio [OR] 3.3, 95% confidence interval [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 only 0.9%. 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 the ZigZag pattern is an early sign of fetal hypoxia, which emphasizes its clinical importance.

The Goal of Continuous Fetal Heart Rate Monitoring During Labor: Have We Been Successful?

Despite its ubiquitous use, fetal heart rate (FHR) monitoring has not resulted in a significant reduction in hypoxic-ischemic encephalopathy following delivery. This manuscript reviews the reasons for this failure including limitations of FHR to accurately predict hypoxia, low prevalence of hypoxic-ischemic encephalopathy, and lack of standardization of interpretation and intervention. We propose an alternative goal for FHR monitoring during labor to provide optimal care by early identification of truly concerning features, initiation of appropriate interventions, clear documentation of concerns and plans, and clear communication between team members on labor and delivery, including initiation of the chain of command as needed.

Identification of the Fetus at Risk for Metabolic Acidemia Using Continuous Fetal Heart Rate Monitoring.

The fetal heart rate can be used to assess the current metabolic state of the fetus and predict the risk of the evolution of metabolic acidemia through the course of labor. In this chapter, we will present the pathophysiology of the development of fetal acidemia and provide an organized approach to identifying the risk of worsening acidemia using changes noted in the fetal heart rate pattern to allow for interventions that might alter this course.

Effectiveness of fetal scalp stimulation test in assessing fetal wellbeing during labor, a retrospective cohort study.

BACKGROUND: It is discussed whether fetal scalp stimulation (FSS) test is a reliable complimentary tool to cardiotocography (CTG) to assess fetal wellbeing during labor. The test is based on the assumption that a well-oxygenated fetus, in contrast to the depressed fetus, will respond to a certain stimulus. The aim of this study was to investigate the effectiveness of the FSS-test. METHODS: A retrospective observational study carried out Copenhagen University Hospital, Herlev, Denmark. Laboring women with singleton pregnancies in cephalic presentation after gestation week 33 and indication for fetal blood sampling (FBS) were eligible for inclusion. The FSS-test was classified as positive when an acceleration was absent at the time of FBS and negative when an acceleration was present. Lactate in scalp blood was measured by the point-of-care device LactatePro™ and pH in artery umbilical cord blood by the stationary blood gas analyzer ABL800. Lactate level < 4.2 mmol/L in scalp blood and arterial cord pH > 7.1 were cut-offs for normality. RESULTS: Three hundred eighty-five women were included. The cohort was divided by the FBS-to-delivery time: Group 1 (n = 128) ≤ 20 min, Group 2 (n = 117) 21-59 min and Group 3 (n = 140) ≥ 60 min. The proportion of FSS-positive tests differed significantly between the groups (p < 0.000). In Group 1 the sensitivity, specificity and likelihoods for scalp lactate ≥4.2 mmol/L were 81.5 (95% CI 67-90.1), 13.3 18.5 (95% CI 5.9-24.6), LHR+ 0.94 (95% CI 0.8-1.1) and LHR - 1.4 (95% CI 0.6-3.2) and for umbilical artery pH ≤ 7.10 the values were 82.6% (95% CI 61.2-95.1), 16% (95% CI 9.4-24.7), 1.0 (95% CI 0.8-1.2) and 1.1 (95% CI 0.4-3) respectively. Regardless of the FBS-to-delivery time the LHR+ for lactate ≥4.2 mmol/L increased to 1.38 (95% CI 1.2-1.6). CONCLUSION: The effectiveness of scalp stimulation test was poor for both ruling in and out fetal hypoxia during labor. Absence of a provoked acceleration seems to be a normal phenomenon in the second stage of labor.

Is obesity in pregnancy associated with signs of chronic fetal hypoxia?

INTRODUCTION: The prevalence of obesity in pregnancy is increasing worldwide. Maternal obesity increases risks of severe fetal and neonatal complications. The underlying pathophysiological mechanisms are unclear. One possible contributing factor could be chronic fetal hypoxia. The aim of this study was to compare placentas from women with and without obesity with respect to placental lesions, which could reflect compensatory mechanisms in response to chronic fetal hypoxia as well as lesions possibly leading to chronic fetal hypoxia. In addition, levels of erythropoietin in cord blood were compared between offspring of lean and obese women. MATERIAL AND METHODS: This cohort study included 180 women with uneventful, full-term, singleton pregnancies, out of which 91 lean women had a body mass index (BMI) of 18.5-24.9 kg/m2 and 89 women had obesity (BMI ≥30 kg/m2 ). Women were recruited at Södersjukhuset between 16 October 2018 and 2 December 2019. Placentas were investigated by two senior perinatal pathologists, who were blinded for maternal BMI. Cord blood was analyzed for levels of erythropoietin. RESULTS: Levels of erythropoietin in cord blood increased with maternal BMI (P = .01, ß = 0.97, 95% CI 0.27-1.68). There was no difference between placentas of obese and lean women in number of placental lesions reflecting chronic fetal hypoxia or in lesions that could possibly lead to chronic fetal hypoxia. CONCLUSIONS: This study of term and uneventful pregnancies demonstrated a positive association between maternal obesity and concentrations of erythropoietin in cord blood at birth. This finding supports the hypothesis of chronic fetal hypoxia as a risk factor for complications in the pregnancies of obese women. There were no differences in lesions associated with hypoxia between placentas of obese and lean women.