Date of Award


Document Type

Campus Access Thesis


Epidemiology and Biostatistics



First Advisor

Jihong Liu


"Objectives:" To investigate whether maternal obesity before pregnancy is a risk factor of delivery of an infant with neural tube defect (NTD) and to study relationships between folic acid intake during the periconceptional period and the risk of NTD in overweight and non-overweight women.

"Methods:" We used data from a state-wide case-control study conducted between 1992 and 1997 in South Carolina. Overall, 179 women with NTD-affected pregnancies (first isolated NTDs, from singleton pregnancies, live born or electively terminated) and 288 women without NTD-affected births were interviewed within 6 months after delivery or pregnancy termination. Average daily intake of supplemental folic acid was estimated based on self-reported brand, dose and frequency of vitamin intake. Folate intake from food was assessed using food frequency questionnaire.

"Results:" After adjustment for confounders including vitamin use in the three months before and after conception, obese women (BMI¡Ý30) had two times higher odds of having NTD-affected pregnancy (odds ratios = 2.04, 95% confidence interval (CI) = 1.09, 3.81) than normal weight women. Compared to the lowest quartile of average daily folate intake from food, women with the upper three quartiles had lower odds of NTDs in offspring. The NTD-protective effect was stronger in overweight and obese women [BMI¡Ý25] than normal weight women (BMI

"Conclusions:" Maternal obesity is a risk factor for NTDs in offspring. Yet higher level of folate intake is NTD-protective and has a stronger effect among overweight and obese women. Obese women should receive advice on weight loss and folate intake.