Maternal obesity, folate intake, and neural tube defects in offspring.

BACKGROUND: We investigated the association between maternal obesity (body mass index [BMI] ≥ 30) and the risk of a neural tube defect affected pregnancy (NTD). We also studied relationships between perinatal folate intake from food and the NTD risk by maternal BMI.

METHODS: Data came from a state-wide case-control study conducted between 1992 and 1997 in South Carolina including 179 women with NTD-affected pregnancies and 288 women without NTD-affected births. A majority of case mothers (77%) and controls (86%) were interviewed within 6 months after delivery or pregnancy termination. Logistic regression models were used to examine the association between maternal obesity and the NTD risk after adjusting for maternal race, age, education, smoking, alcohol/drug use, chronic conditions, and multivitamin use within six periconceptional months. Stratified analysis by maternal BMI (≥25 vs. <25) was conducted for the association between food folate and the NTD risk.

RESULTS: After adjustment for confounders, obese women (BMI ≥ 30) had twice higher odds of having an NTD-affected pregnancy (odds ratios [OR] = 2.06, 95% confidence interval [CI] = 1.12, 3.81) than normal weight women (BMI: 18.0-24.9). Compared to the lowest quartile of average daily folate intake from food, the upper three quartiles had lower odds of NTDs in offspring. The NTD-protective association was stronger in overweight/obese women (BMI ≥ 25) than in normal/underweight women (BMI < 25).

CONCLUSIONS: These results support previous studies suggesting maternal obesity as a risk factor for NTDs. Higher intakes of dietary folate were associated with decreased NTD risk that was stronger in overweight and obese women.