Association between body mass index and folate insufficiency indicative of neural tube defects risk among nonpregnant women of childbearing age in the United States, NHANES, 2007-2010.

Background: Maternal folate status and obesity are known risk factors for neural tube defects (NTD) in the offspring. We examined the association between body mass index (BMI) categories and blood folate concentrations, specifically, red blood cell (RBC) folate concentrations indicative of NTD risk among nonpregnant women of child-bearing age (20-44 years) in the United States.

Methods: We used data from 2007 to 2010 US National Health and Nutrition Examination Survey (NHANES). Overweight, obesity, and strata within obesity were examined. Serum and RBC folate concentrations were examined as continuous and categorical variables. RBC folate concentrations were grouped indicating high (≤585 nmol/L) and elevated risk (586-747 nmol/L) for NTDs. Unadjusted and adjusted prevalence odds ratios (aPOR) and their 95% confidence intervals (CI) were estimated using logistic regression.

Results: Of the 30,878 participants, 25.6% were overweight, 32.7% obese, and 32.3% had RBC folate concentration indicating NTD risk (<748 nmol/L). Overweight was not associated with RBC folate level for NTD risk; however, a marginally significant negative association was noted for overall obesity and RBC folate concentrations indicative of elevated NTD risk (aPOR = 0.76; 95% CI = 0.45, 1.00). A significant protective association was noted between Class 3 obesity (BMI ≥40 kg/m ) and folate concentration indicative of high NTD risk (≤585 nmol/L; aPOR = 0.46; 95% CI = 0.24, 0.89).

Conclusions: The prevalence of RBC folate concentrations indicating elevated or high NTD risk varied by level of obesity among nonpregnant women of child-bearing age. Further studies are needed to understand the folate pathway in overweight and obese women and subsequent NTD risk in their offspring.