Multivitamin use and the risk of preterm birth.

Previous research suggests that multivitamin use before and during pregnancy can diminish diet-related deficiencies of certain micronutrients and potentially prevent preterm birth. To assess this association, the authors performed an analysis by using data from the Pregnancy, Infection, and Nutrition Study (n = 2,010). Women were recruited at 24-29 weeks of pregnancy from four prenatal care clinics in North Carolina from August 1995 to June 2000. For women who took multivitamins prior to pregnancy, compared with nonusers, the adjusted risk ratio was 0.50 (95% confidence interval: 0.20, 1.25) for delivering preterm (<37 weeks). In contrast, prenatal and periconceptional use, compared with nonuse, were not related to preterm birth, with adjusted risk ratios of 1.1. Preconceptional multivitamin use was inversely associated with both early (<35 weeks; adjusted odds ratio = 0.59, 95% confidence interval: 0.12, 2.76) and late (35-36 weeks; adjusted odds ratio = 0.40, 95% confidence interval: 0.12, 1.40) preterm birth; findings were based on only two and three exposed cases, respectively. These results suggest that, compared with nonusers, women who take multivitamin supplements prior to conception may have a reduced risk of preterm birth, but further studies are needed with a larger sample of preconceptional users.