Objective: To evaluate the relationship of fetal sex with obstetric risk factors and perinatal outcomes.
Material and methods: Retrospective study of deliveries during 2003-2009 at a tertiary hospital based on the analysis of obstetric and neonatal risk variables according to neonatal sex.
Results: Of the 29,530 deliveries studied, the neonate was a boy in 15,038 (50.92%) and a girl in 14,492 (49.08%). The rates of gestational diabetes, prematurity, true umbilical cord knot and nuchal cord were higher for male newborns, whereas the rate of echographic diagnosis of intrauterine fetal growth retardation was higher for female newborns. Mothers of male fetuses had higher rates of cesarean delivery and instrumental vaginal delivery. The indication for ending labor due to the non-reassuring fetal heart rate was also more frequent among male newborns. This group had higher rates of acidemia, although there were no significant differences between sexes in other short-term neonatal outcomes. In all subgroups analyzed here, fetal weight was higher in male newborns.
Conclusions: Male sex is an independent risk factor for unfavorable outcomes of pregnancy and delivery.