Folic acid supplementation, dietary folate intake during pregnancy and risk for spontaneous preterm delivery: a prospective observational cohort study.
Health authorities in numerous countries recommend periconceptional folic acid supplementation to prevent neural tube defects. The objective of this study was to examine the association of dietary folate intake and folic acid supplementation during different periods of pregnancy with the risk of spontaneous preterm delivery (PTD).
The Norwegian Mother and Child Cohort Study is a population-based prospective cohort study. A total of 66,014 women with singleton pregnancies resulting in live births in 2002-2009 were included. Folic acid supplementation was self-reported from 26 weeks before pregnancy until pregnancy week 24. At gestational week 22, the women completed a food frequency questionnaire, which allowed the calculation of their average total folate intake from foods and supplements for the first 4-5 months of pregnancy. Spontaneous PTD was defined as the spontaneous onset of delivery between weeks 22+0 and 36+6 (n = 1,755).
The median total folate intake was 313 µg/d (interquartile range IQR 167-558) in the overall population and 530 µg/d (IQR 355-636) in the supplement users. Eighty-five percent reported any folic acid supplementation from