Background: During labour, severe, prolonged, or frequent hypoxia can lead to hypoxic-ischemic encephalopathy (HIE), potentially causing brain injury or death.
Objective: Investigate how maternal fever affects fetal heart rate (FHR) in labour and its association with HIE.
Methods: We analysed maternal temperature, FHR, and uterine contraction data from a retrospective cohort of singleton infants (≥35 weeks) delivered at 16 Northern California Kaiser Permanente hospitals (2011–2019). PeriGen Patterns was used to obtain FHR patterns (baseline, decelerations, accelerations). Outcomes were classified into four groups based on umbilical cord or early infant blood gas results, neurological exams, and clinical interventions: (1) HIE, (2) Acidosis Alone, (3) Healthy, No Acidosis, (4) Presumed Healthy. Data were stratified by the presence of intrapartum fever (≥38°C). A linear mixed-effect model was used to model the relationship between FHR and maternal temperature, adjusting for labour progress, epidural administration, hospital site, and pregnancy.
Results: In the fever group, all outcome classes showed statistically significant increases in baseline FHR and deceleration time compared to before fever. Differences in baseline FHR between the HIE and Healthy outcome classes were larger for increasing temperature.
Conclusion: These findings highlight the need to consider fever status when defining clinical guidelines or developing machine learning models based on FHR data.