Association between prepregnancy body mass index and risk of congenital heart defects in offspring: an ambispective observational study in China

BACKGROUND: Congenital heart defects (CHDs) are the most common birth defect around the world. Maternal prepregnancy obesity has been proposed as a risk factor of CHDs, but the relationship of CHD risk with over- and underweight is controversial, especially because body mass index (BMI) distribution differs between Asia and the West. The study aimed to examine the potential associations of maternal over- and underweight on risk of offspring CHDs. METHODS: An ambispective observational study involving 1206 fetuses with CHDs and 1112 fetuses without defects at seven hospitals in China was conducted. Standardized questionnaires were used to collect information on maternal prepregnancy weight and height, social demographic characteristics, living and occupational environments, and lifestyle behaviors. Univariate, multivariate and multilevel logistic regression as well as unrestricted cubic spline analysis were used to examine potential associations of prepregnancy BMI and offspring CHDs. RESULTS: Prepregnancy maternal underweight (BMI<18.5) or low average BMI (18.5 ≤ BMI<21.25) was associated with significantly higher risk of CHD in offspring than high average BMI (21.25 ≤ BMI<24.0): multilevel logistic regression indicated adjusted odds ratios of 1.53 (95%CI 1.13, 2.08) for underweight, 1.44 (95%CI 1.10, 1.89) for low average BMI and 1.29 (95%CI 0.84, 1.97) for overweight or obesity (BMI ≥ 24.0). Mothers with prepregnancy BMI < 21.25 were at greater risk of offspring with septal defects, while mothers with low average BMI were at greater risk of offspring with conotruncal defects and septal defects. CONCLUSIONS: Our findings suggest that underweight or low average BMI may be associated with higher risk of CHDs in offspring. Health professionals may wish to advise women planning to be pregnant to maintain or even gain weight to ensure adequate, balanced nutrition and thereby reduce the risk of CHDs in their offspring.