Prepregnant maternal obesity increases risk of several congenital anomalies, in particular neural tube defects, in the offspring.

Background: Overweight and obesity are a growing health problem. Several studies have shown an association between a high maternal body mass index (BMI) before pregnancy and some congenital anomalies. However, research on this topic has never been applied to the Dutch population. The aim of this case-control study is to investigate the relationship between a high prepregnant maternal BMI and various major congenital anomalies in the Northern Netherlands. Methods: 4513 cases and 1693 (malformed) controls born between 1997 and 2010, with known maternal BMI data, were identified from the EUROCAT registration. Univariate and multivariate logistic regression with BMI in four and additionally in six categories was conducted. Potential confounders included smoking, maternal age, educational level, folic acid use, history of pregnancies affected with congenital anomaly, diabetes and interaction between smoking and BMI. Results: We found an increased risk for obese women compared to normal weight women of having a child with a neural tube defect (adjusted odds ratio [aOR]: 2.41; 95% confidence interval [CI]: 1.46 – 3.98), especially thoracic spina bifida (aOR: 5.66; CI: 2.04 – 15.65), cleft palate (aOR: 2.06; CI: 1.16 – 3.65), congenital malformation of oesophagus (aOR: 2.94; CI: 1.37 – 6.31), urinary anomaly (aOR: 1.68; CI: 1.18 – 2.38), especially cystic kidney (aOR: 2.84; CI: 1.46 – 5.51) and deformity of foot (aOR: 1.90; CI: 1.21 – 2.99). Conclusion: This study has shown that obese women are at greater risk of having a child with specific major congenital anomalies, especially neural tube defects. Given the fact that the number of overweight and obese women is rising, our findings are important for public health.