Maternal folate status, but not that of vitamins B-12 or B-6, is associated with gestational age and preterm birth risk in a multiethnic Asian population.

BACKGROUND Maternal folate, vitamin B-12, and vitamin B-6 concentrations during pregnancy have been shown to influence birth outcomes, but the evidence is inconclusive. OBJECTIVE We aimed to examine the associations of maternal B-vitamin status with gestational age, birth weight, and length in a birth cohort study in Singapore. METHODS Maternal blood samples (n = 999) collected during weeks 26-28 of gestation were assayed for plasma folate, vitamin B-12, and vitamin B-6 concentrations. Birth weight and gestational age data were obtained from hospital records, and other anthropometric variables were measured within 72 h after birth. Relations between B-vitamin status and birth outcomes were assessed by linear or logistic regression with adjustment for potential confounders. RESULTS Median (IQR) plasma concentrations were 34.4 (24.5-44.6) nmol/L for folate, 209 (167-258) pmol/L for vitamin B-12, and 61.8 (25.9-113) nmol/L for vitamin B-6. We found that higher plasma folate concentrations were associated with a longer gestational age (0.12 wk per SD increase in folate; 95% CI: 0.02, 0.21) and tended to be associated with lower risk of all preterm birth (delivery at <37 wk of gestation; OR: 0.79; 95% CI: 0.63, 1.00) and spontaneous preterm birth (OR: 0.76; 95% CI: 0.56, 1.04). Overall, concentrations of maternal folate, vitamin B-12, and vitamin B-6 were not independently associated with birth weight or being born small for gestational age (SGA; birth weight <10th percentile for gestational age). CONCLUSIONS Higher maternal folate concentrations during late pregnancy were associated with longer gestational age and tended to be associated with a lower risk of preterm birth in this multiethnic Asian population. In contrast, the results of our study suggested little or no benefit of higher folate concentrations for reducing the risk of SGA or of higher vitamin B-6 and vitamin B-12 concentrations for reducing the risk of preterm birth or SGA.