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Observational studies suggest that premature delivery is associated with low folate concentrations during pregnancy. Investigators prospectively examined the association between preconceptual folate supplementation and risk for spontaneous preterm birth in a U.S. cohort of 34,480 low-risk singleton pregnancies. First-trimester ultrasound was used to estimate the duration of pregnancy.
Folate supplementation was reported by 20% of women for 1 year or longer and by 36% for less than 1 year; 44% did not report taking folate. Spontaneous premature delivery (before 37 weeks' gestation) that was not caused by medical or obstetrical complications occurred in 1818 women. Compared with no folate supplementation, preconceptual folate supplementation for 1 year or longer was associated with a 70% reduction in risk for spontaneous preterm delivery between 20 and 28 weeks' gestation and a 50% reduction in risk for delivery between 28 and 32 weeks. The association persisted after adjustment for maternal and obstetric characteristics. The risk reduction associated with supplementation for less than 1 year did not reach statistical significance.
Bukowski R et al. Preconceptional folate supplementation and the risk of spontaneous preterm birth: A cohort study. PLoS Med 2009 May 5; 6:e1000061. (http://dx.doi.org/10.1371/journal.pmed.1000061)
Comment
Preterm births account for a significant proportion of visual impairment, mental retardation, and cerebral palsy. The authors note that the societal cost of preterm births in the U.S. exceeds $26 billion annually, and no effective preventive therapy is currently available. While the role of preconceptional folate supplementation for prevention of neural tube defects is well established, folic acid fortification of grains in North America is generally considered inadequate to prevent at least 50% of folate-preventable congenital anomalies. This level of fortification is probably also inadequate for prevention of prematurity. Although the mechanism for prevention of preterm delivery is unclear, the effects in this study persisted after adjustment for maternal and obstetric factors and therefore seem real. These new data provide clinicians with an additional reason to encourage all women to take multivitamin supplements during their reproductive years.