Racial and ethnic differences in predictors of vitamin D among pregnant women in south-eastern USA

Insufficient vitamin D during pregnancy increases risk of adverse outcomes, with known differences by race/ethnicity. We sought to determine whether predictors of vitamin D insufficiency vary by race/ethnicity in an ethnically diverse pregnancy cohort. Plasma 25-hydroxyvitamin D concentrations and patient characteristics were measured at first prenatal visit to prenatal clinics in south-eastern USA between 2009 and 2011 (n 504). Prevalence ratios (PR) and 95 % CI were estimated using multivariable regression to quantify predictors of vitamin D insufficiency, overall and by race/ethnicity. In race/ethnicity-stratified models, season was most associated with vitamin D insufficiency among non-Hispanic white women; PR for winter v. summer were 3 center dot 58 (95 % CI 1 center dot 64, 7 center dot 81) for non-Hispanic white, 1 center dot 52 (95 % CI 1 center dot 18, 1 center dot 95) for Hispanic and 1 center dot 14 (95 % CI 0 center dot 99, 1 center dot 30) for non-Hispanic black women. Although women with darker skin tones are most vulnerable to prenatal vitamin D insufficiency, season may be more strongly associated with insufficiency among women with lighter skin tones.