Effect of folic acid supplementation on preterm delivery and small for gestational age births: A systematic review and meta-analysis.

OBJECTIVE: To investigate the effect of folic acid (FA) supplementation on the risks of preterm delivery (PTD) and small for gestational age births (SGA).

DATA SOURCES: Cohort studies were identified from MEDLINE, EMBASE, the Cochrane Library, CINAHL, and CBM from inception to January 2015.

PARTICIPANTS AND INCLUDED STUDIES: Healthy women who want to get pregnancy or being pregnant.

MAIN OUTCOME MEASURES: PTD and SGA.

RESULTS: The association of FA and PTD was significant when supplement initiated after pregnancy (RR=0.68, 95%CI, 0.52-0.90), whereas no effect was founded if the initiation time was before conception (RR=0.89, 95%CI, 0.80-1.01). The results for the association between FA supplementation and SGA showed significant protective effect: initiated before conception (RR=0.70, 95%CI, 0.57-0.85) and initiated after conception (RR=0.84, 95%CI, 0.81-0.89).

CONCLUSION: Folic acid supplementation is associated with a significant reduction on the risk of PTD when initiated after conception. It can also protect fetus from SGA.