Fetal sex and maternal risk of gestational diabetes mellitus: the impact of having a boy.

OBJECTIVE Retrospective analyses of perinatal databases have raised the intriguing possibility of an increased risk of gestational diabetes mellitus (GDM) in women carrying a male fetus, but it has been unclear if this was a spurious association. We thus sought to evaluate the relationship between fetal sex and maternal glucose metabolism in a well-characterized cohort of women reflecting the full spectrum of gestational glucose tolerance from normal to mildly abnormal to GDM. RESEARCH DESIGN AND METHODS A total of 1,074 pregnant women underwent metabolic characterization, including oral glucose tolerance test (OGTT), at mean 29.5 weeks' gestation. The prevalence of GDM, its pathophysiologic determinants (β-cell function and insulin sensitivity/resistance), and its clinical risk factors were compared between women carrying a female fetus (n = 534) and those carrying a male fetus (n = 540). RESULTS Women carrying a male fetus had lower mean adjusted β-cell function (insulinogenic index divided by HOMA of insulin resistance: 9.4 vs. 10.5, P = 0.007) and higher mean adjusted blood glucose at 30 min (P = 0.025), 1 h (P = 0.004), and 2 h (P = 0.02) during the OGTT, as compared with those carrying a female fetus. Furthermore, women carrying a male fetus had higher odds of developing GDM (odds ratio 1.39 [95% CI 1.01-1.90]). Indeed, male fetus further increased the relative risk of GDM conferred by the classic risk factors of maternal age >35 years and nonwhite ethnicity by 47 and 51%, respectively. CONCLUSIONS Male fetus is associated with poorer β-cell function, higher postprandial glycemia, and an increased risk of GDM in the mother. Thus, fetal sex potentially may influence maternal glucose metabolism in pregnancy.