Prepregnancy overweight and obesity as risk factors for birth defects: a cross-sectional study over a 30-year period

Overweight and obesity are public health problems worldwide despite being modifiable conditions. The association between birth defects and pregestational maternal body mass index is not entirely clear. We aimed to assess the prevalence and estimate the risk of birth defects related to pregestational body mass index and other maternal factors. We explored a 30-year time series database in a cross-section study. We analysed 40,217 cases, among them 2.8% had birth defects. Bivariate analysis showed a higher prevalence of birth defects with increased pre-pregnancy body mass index and in extremes of maternal age, white skin colour, and primiparity. Multivariable logistic regression showed a higher chance of birth defects in women with pre-pregnancy overweight/obesity (OR:1.19 [CI95%:1.01-1.41]), maternal age ≥ 40 years (OR:1.68 [CI95%:1.11-2.54]), and white skin colour (OR:1.44 [CI95%:1.19-1.75]). Maternal weight is a modifiable risk factor that must be considered and addressed in preconception counselling to minimise possible deleterious effects on embryogenesis.IMPACT STATEMENTWhat is already known on this subject? Previous studies have linked some maternal factors with birth defects. However, the association with prepregnancy maternal body mass index is not clear.What do the results of this study add? Our findings provide support for the association of prepregnancy maternal overweight and obesity with birth defects and highlight that BMI is a modified risk factor.What are the implications of these findings for clinical practice and/or further research? Maternal body mass index is a modifiable risk factor, highlighting the importance of preconception counselling for the prevention and possible reduction of factors that increase the risk of birth defects.