The Relationship of Antepartum Fetal Heart Rate Patterns to Adverse Pregnancy Outcomes

Abstract

Introduction: Antepartum fetal heart rate (FHR) patterns are routinely assessed using to evaluate fetal well-being. Despite their clinical use, the relationship between specific FHR patterns and adverse pregnancy outcomes (APOs) remains unclear. This study aims to investigate the association between antepartum FHR patterns and APOs to improve fetal risk assessment. Methods: In this retrospective case-control study, we extracted raw antepartum FHR traces from singleton pregnancies between 27⁺⁰ and 41⁺⁶ weeks' gestation recorded at Oxford University Hospitals from January 1991 to February 2024. Adverse outcomes included acidaemia, stillbirth, asphyxia, extended neonatal care unit (NCU) admission, hypoxic-ischaemic encephalopathy (HIE), low Apgar scores and neonatal resuscitation at delivery. After applying inclusion and exclusion criteria, 938 FHR traces with APOs were matched using propensity score matching with 938 traces from normal pregnancy outcomes (NPOs), controlling for gestational age, fetal sex, maternal BMI, maternal age, parity, and trace duration. FHR patterns were extracted using a validated automated algorithm and analysed statistically. Results: The APO cohort showed significantly higher basal heart rates (BHR), fewer accelerations, more decelerations, lower short-term variability (STV), and spent a greater proportion of the trace in periods of low variation compared to the NPO cohort (p < 0.001). Logistic regression identified prolonged periods of low variation (odds ratio [OR] = 1.92, 95% CI 1.60-2.30), increased decelerations (OR = 1.40, 95% CI 1.22-1.60), reduced accelerations (OR = 0.66, 95% CI 0.55-0.78), elevated BHR (OR = 0.70, 95% CI 0.61-0.80), and decreased STV (OR = 0.72, 95% CI 0.57-0.91) as significant predictors of APOs. Conclusions: Specific antepartum FHR patterns are significantly associated with adverse pregnancy outcomes. Detailed analysis of these patterns can enhance fetal risk assessment and inform clinical decision-making. Adoption of standardised interpretation criteria for antepartum FHR monitoring may improve perinatal outcomes.