Fetal Sex Differences in Intrapartum Electronic Fetal Monitoring

Objective The article aimed to estimate differences in electronic fetal monitoring (EFM) patterns in term gestations attributable to fetal sex. Study Design We conducted a prospective cohort study of consecutive, singleton, nonanomalous, term gestations that labored during admission. EFM characteristics in the 30 minutes prior to delivery were evaluated. Logistic regression models estimated adjusted risks for EFM features by sex. To further estimate the impact of sex, we limited the analysis to gestations without composite morbidity (morbidity defined as arterial cord pH <7.20, 5-minute Apgar <7, or neonatal intensive care unit admission). Results Of 2,639 deliveries, 1,400 (53%) were male. Male fetuses had a higher number of decelerations (median [interquartile range]: 8 [5, 11] vs. 7 [4, 10], p < 0.003) and increased total deceleration area (adjusted odds ratio [aOR]: 1.11, 95% confidence interval [CI]:1.04, 1.18). Male fetuses were at increased risk for prolonged decelerations (aOR: 1.21, 95% CI: 1.03, 1.42) and repetitive variable decelerations (aOR: 1.24, 95% CI: 1.05, 1.47). Among neonates without composite morbidity (n = 2,446, 92.7%), male sex conferred an increased risk of late decelerations (aOR: 1.21, 95% CI: 1.02, 1.43) and increased total deceleration area (aOR: 1.12, 95% CI: 1.05, 1.20). Conclusion There are significant sex differences in EFM patterns at term among pregnancies without evidence of acidemia. This suggests that interpretation of EFM patterns may need to take into account factors such as fetal sex.