Fetal and Neonatal Heart Rate Trends in Preterm Delivery: A Clinical Study from the Week before to the Week after Birth

This study aimed to explore the fetal heart rate trend in the week before birth, the transition from fetal to neonatal heart rate, and the neonatal heart rate trend in the week after birth in preterm neonates admitted to a tertiary care hospital, considering maternal and neonatal factors. A retrospective cohort study was conducted, including neonates born between 24 and 34 weeks of gestation. Baseline heart rate, average deceleration capacity, standard deviation, skewness, and sample entropy were assessed using interrupted time series and difference-in-differences analyses. Subgroup analyses were performed according to gestational age at birth, sex, birth weight, mode of delivery, Apgar score at 5 minutes, umbilical cord pH, and neonatal medication. The fetal and neonatal heart rate of 123 patients was analyzed. After birth, step change of baseline (2.23 bpm, p < 0.05), average deceleration capacity (0.43 bpm, p < 0.001), and skewness (0.47 nu, p < 0.001) increased, while sample entropy (−0.68 bits, p < 0.001) and standard deviation (−1.15 bpm, p < 0.001) decreased. Postnatally, baseline increased in linear slope and decreased in quadratic slope (both p < 0.001). Average deceleration capacity decreased in linear slope (p < 0.001). Sample entropy and standard deviation increased in linear slopes (both p < 0.001). Skewness increased in quadratic slope (p < 0.05). Subgroup analyses revealed that delivery mode, medication, and birth weight modulated these trends. This study provides unique insights into heart rate frequency and variability trends during the period around preterm birth. It highlights the dynamic physiological adaptation that occurs during the transition from intrauterine to extrauterine life in preterm infants and may help inform future research on fetal and neonatal monitoring and clinical management.