The influence of fetal sex on preterm birth risk in gestational diabetes mellitus: A retrospective cohort study

Gestational diabetes mellitus (GDM), a condition characterized by glucose intolerance first recognized during pregnancy, is associated with adverse maternal and neonatal outcomes such as preterm birth. To investigate whether fetal sex influences the risk of preterm birth among women with GDM, a retrospective cohort study was conducted at The Affiliated Hospital, Southwest Medical University (Luzhou, China), between January 2019 and December 2022. A total of 424 women with singleton pregnancies diagnosed with GDM according to the American Diabetes Association criteria were included. Participants were divided into a male fetus group (n=212) and a female fetus group (n=212). Preterm birth was defined as delivery before 37 completed weeks of gestation. Statistical analyses included unadjusted group comparisons, multivariable logistic regression, sensitivity analyses, propensity score matching (PSM) and subgroup analyses to account for potential confounders. Analysis revealed that the incidence of preterm birth was higher in the male fetus group (19.3%) than in the female fetus group (14.2%), although the difference was not statistically significant (P=0.172). Multivariable logistic regression showed that fetal sex was not an independent risk factor for preterm birth (OR=1.35; 95% CI=0.85-2.15; P=0.209). Sensitivity analyses stratified by GDM severity and glycemic control status demonstrated no significant differences in preterm birth risk by fetal sex across subgroups. PSM confirmed the adequate balance of baseline characteristics and the difference in preterm birth risk between groups remained non-significant after adjustment. Subgroup analyses further indicated that maternal age, BMI and glycemic control status did not significantly modify the association between fetal sex and preterm birth risk. Overall, although pregnancies with male fetuses were delivered at a slightly earlier gestational age, fetal sex did not independently increase the risk of preterm birth in women with GDM after adjustment for maternal and clinical factors. These findings indicated that, in this population, preterm birth risk was primarily driven by maternal metabolic and clinical characteristics rather than fetal sex, underscoring the importance of focusing on established predictors in clinical management.