738 Sex-specific differences in electronic fetal monitoring patterns

Abstract

Fetal male sex is associated with worse neonatal outcomes, but etiology of this phenomenon is not well elucidated. It has been hypothesized that males have an increased cytokine response and decreased catecholamine response to traumatic events, which could suggest a decreased tolerance of labor and therefore be detected in electronic fetal monitoring (EFM) patterns. We sought to determine if there were differences in EFM features in the 60 minutes prior to delivery. We performed a secondary analysis of a prospective cohort study of low risk women (excluding those with hypertensive disorder or diabetes) with a singleton fetus admitted for labor at term between 2010 to 2014 in a single institution. Baseline characteristics were compared between mothers of male and female infants. The primary outcome was EFM characteristics in the 60 minutes before delivery. Multivariable logistic regression was performed to determine the relationship between fetal sex and EFM characteristic while adjusting for confounders. Of the 4,055 low risk patients, 2,074 (51%) delivered a male infant. Mothers of male fetuses were more likely to go into spontaneous labor (p=0.02), but rates of operative vaginal (5.6 vs 4.1%, p=0.04) and cesarean delivery (CD) (18.1 vs 14.0%, p<0.01) and non-reassuring fetal status as indication for delivery (18.1vs 14.0%, p<0.01) were higher among males. Males were more likely to have bradycardia, recurrent variable decelerations, and higher total deceleration area and were less likely to have tachycardia compared to females. Males had higher odds of decelerations and bradycardia, but females had higher odds of tachycardia, possibly due to improved ability to generate a catecholamine response. Cesarean deliveries for non-reassuring fetal status are more common in pregnancies with male fetuses. These data suggest males are less likely to tolerate stresses of labor, which may drive the difference in mode of delivery and at least partially explain the increased morbidity male neonates experience.