Maternal obesity is associated with a wide range of risks and complications, including preeclampsia, cesarean delivery, and adverse offspring outcomes. This study aims to investigate the associations between maternal obesity and the risk of congenital malformations in offspring.

This population-based cohort study included a total of 1,243,957 live-born singleton infants born to mothers who were underweight (BMI<18.5)), overweight (BMI 25 to <30), obese-I (BMI 30 to <35), obese-II (BMI 35 to <40), or obese-III (BMI≥40). The offspring were evaluated corresponding to maternal BMI and the first prenatal visit. The primary outcome of the study was major congenital malformation in offspring, along with organ-specific malformations.

Of 1,243,957 live-born singleton infants, 43,550 (3.5%) had a major congenital malformation, with most common subgroup being congenital heart defects (n=20,074 [1.6%]). When compared with the offspring of normal weight mothers, the adjusted risk ratios of a major congenital malformation were overweight: 1.05, obesity-I: 1.12, obesity-II: 1.23, obesity-III: 1.23. The proportions for congenital malformation in the aforementioned obesity classes were 3.5%, 3.8%, 4.2%, and 4.7%, respectively.

The research concluded that maternal obesity was associated with a higher risk of congenital malformation in offspring, with the risk being linearly associated with the severity of obesity.