The association of maternal dietary folate intake and folic acid supplementation with small-for-gestational-age births: a cross-sectional study in Northwest China.

The effect of maternal folate intake on small-for-gestational-age (SGA) births remains inconclusive. The present study aimed to investigate the associations of maternal folate intake from diet and supplements with the risk of SGA births using data from a cross-sectional study in Shaanxi Province of Northwest China. A total of 7307 women who were within 12 months (median 3; 10th-90th percentile 0-7) after delivery were included. Two-level models were adopted to examine the associations of folate (dietary folate, supplemental folic acid and total folate) intake with the risk of SGA births and birth weight Z score, controlling for a minimum set of confounders that were identified in a directed acyclic graph. Results showed that a higher supplemental folic acid intake during the first trimester was negatively associated with the risk of SGA births (<= 60 d v. non-use: OR 0 center dot 80; 95 % CI 0 center dot 66, 0 center dot 96; >60 d v. non-use: OR 0 center dot 78; 95 % CI 0 center dot 65, 0 center dot 94; P-trend = 0 center dot 010; per 10-d increase: OR 0 center dot 97; 95 % CI 0 center dot 95, 0 center dot 99). A higher total folate intake during pregnancy was associated with a reduced risk of SGA births (highest tertile v. lowest tertile: OR 0 center dot 77; 95 % CI 0 center dot 64, 0 center dot 94; P-trend = 0 center dot 010; per one-unit increase in the log-transformed value: OR 0 center dot 81; 95 % CI 0 center dot 69, 0 center dot 95). A similar pattern was observed for the birth weight Z score. Our study suggested that folic acid supplementation during the first trimester and a higher total folate intake during pregnancy were associated with a reduced risk of SGA births.