Fetal sex pairing and adverse perinatal outcomes in twin gestations

Abstract

PurposeTo assess the association between fetal sex pairing in twin pregnancies and adverse perinatal and infant outcomes. MethodsA retrospective cohort study of 9770 infants from 4885 twin pregnancies delivered in 2007 was conducted with a statewide hospital discharge database for Texas. Log-binomial regression models based on generalized estimating equations were used to calculate relative risks (RR) and 95% confidence intervals (95% CI) for the following dichotomous outcomes: breech presentation, hospital mortality, intrauterine growth restriction (IUGR), low birth weight, prolonged length of stay (>4 days), receipt of mechanical ventilation, and respiratory distress syndrome (RDS). ResultsThe sample was composed of 4918 females and 4852 males. An approximately equal number of infants were from a female–female pregnancy (n = 3270), mixed-sex pregnancy (n = 3296), and a male–male pregnancy (n = 3204). Twins of either sex from mixed-sex pairs were 45% less likely to die in the hospital compared with females from a female–female pregnancy (RR, 0.55, 95% CI, 0.31–0.98). Males from a male–male pair were 33% less likely than females from female–female pairs to experience IUGR (RR, 0.67; 95% CI, 0.53–0.83). The incidence of RDS was significantly increased in males from male–male twin pairs versus females from female–female pairs (RR, 1.21; 95% CI, 1.05–1.41). ConclusionsMale infants from male–male twin pairs were more likely to develop RDS and be placed on a ventilator but less likely to experience IUGR than female infants from female–female pairs.