Sex matters: Increased adverse perinatal outcome in male fetuses

Objective
To study the association between fetal gender, pregnancy course, and perinatal outcome.

Study Design
This population based retrospective cohort study included all singleton deliveries in a tertiary medical center between the years 1999-2013. A comparison was performed between males and females and included pregnancy characteristics and perinatal outcome. Perinatal mortality cases, fetuses with congenital malformations, and multiple pregnancies, were excluded from the analysis. Multiple logistic regression models were used in order to control for confounders including maternal age and parity.

Results
During the study period 240 953 newborns met the inclusion criteria and were included in the analysis. Of them, 51.0% (n= 122 840) were males and 49.0% (n=118 113) females. Maternal characteristics and pregnancy outcomes of male vs. female newborns are shown in the Table. Mothers of male newborns were younger and delivered at an earlier mean gestational age. Male newborns were significantly more likely to be delivered prematurely (at less than 37 and less than 34 completed weeks’ of gestation), and their mothers were significantly more likely to suffer from gestational diabetes and undergo a cesarean delivery. In the multivariable analysis, while controlling for maternal age and parity, male gender was found to be independently associated with diabetes, preterm delivery (both before 34 and 47 weeks’ gestation), and cesarean delivery (Table).

Conclusion
Male gender is an independent risk factor for adverse pregnancy outcome.