Objectives Despite being encouraged to take pre-natal supplements, suboptimal micronutrient intake is common in pregnancy, especially among Hispanic women. In this study, we assessed whether initiation and timing of pre-natal vitamin use influences the risk of preterm birth. Methods Women who gave birth to singletons in 2003 in Los Angeles County, California, were enrolled into a population-based case-control study. Focusing on non-Hispanic white and Hispanic women, associations between timing of pre-natal supplement use and preterm birth were assessed using logistic regression. Results Among Hispanic mothers, the odds of preterm birth increased the later a woman initiated pre-natal supplement use in pregnancy. The magnitude of this association was larger in US-born compared to foreign-born Hispanic women. Conclusions These findings suggest that nativity may modify the relationship between pre-natal supplement use and preterm birth possibly due to underlying differences in diet composition of Hispanic women by place of birth.
Keywords: Folic acid; Maternal public health; Nutritional epidemiology; Preconception nutrition; Prenatal nutrition; Preterm birth.