Sex-Specific Differences in Neonatal Morbidity at Term [34O

Abstract

INTRODUCTION: Male sex is associated with worse outcomes among preterm neonates, but it is unclear if such sex discordant morbidity occurs in term infants. The aim of this study was to investigate the relationship between fetal sex and neonatal morbidity at term gestation. METHODS: This is a secondary analysis of a prospective cohort of women admitted for labor at term within a single institution from 2010 to 2015. The primary outcome was composite neonatal morbidity that included death, respiratory distress, mechanical ventilation, meconium aspiration syndrome, suspected sepsis, hypoxic-ischemic encephalopathy, therapeutic hypothermia, and seizure. Multivariable logistic regression was used to estimate the association between infant sex and neonatal morbidity. RESULTS: Of the 8578 participants, 51% delivered a male fetus. Birthweight was higher in male infants (3304 g vs 3177 g, P<.01), as were the rates of prostaglandin administration (19.0 vs 11%, P<.01), operative vaginal (4.0 vs 5.6%, P<.01), and cesarean delivery (15.4 vs 18.6%, P<.01). After adjusting for birthweight, male infants had a significantly higher risk of composite neonatal morbidity (aOR 1.21 [95% CI 1.04, 1.40]). This association was driven primarily by a higher rate of respiratory distress in male infants (1.34 [1.07, 1.68]). CONCLUSION: Term male infants appear to be at increased risk for neonatal morbidity compared to females even after adjustment for birthweight. This association was partly driven by a higher rate of respiratory morbidity in male infants. Our findings reinforce the current notion that neonatal outcomes can be sex-dependent, and call for further investigation into the physiologic mechanisms driving this association.