Objectives The study objective was to examine the prevalence of maternal multivitamin use and associations with preterm birth (<37 weeks gestation) in the United States. We additionally examined whether associations differed by race/ethnicity. Methods Using the Pregnancy Risk Assessment Monitoring System, we analyzed 2009-2010 data among women aged ≥18 years with a singleton live birth who completed questions on multivitamin use 1 month prior to pregnancy (24 states; n = 57,348) or in the last 3 months of pregnancy (3 states, n = 5095). Results In the month prior to pregnancy, multivitamin use ≥4 times/week continued to remain low (36.8 %). In the last 3 months of pregnancy, 79.6 % of women reported using multivitamins ≥4 times/week. Adjusting for confounders, multivitamin use 1-3 times/week or ≥4 times/week prior to pregnancy was not associated with preterm birth overall. Though there was no evidence of dose response, any multivitamin use in the last 3 months of pregnancy was associated with a significant reduction in preterm birth among non-Hispanic black women. Conclusions for Practice Multivitamin use during pregnancy may help reduce preterm birth, particularly among populations with the highest burden, though further investigations are warranted.
