Polymorphisms in folate metabolizing genes and risk for spontaneous preterm and small-for-gestational age birth.

Variants in the folate metabolism pathway affect the accumulation of homocysteine are modified by nutrient levels and have been linked to adverse birth outcomes. We examined the relationship among MTHFR(677), MTHFR(1298), MTR(2756), MTRR(66), and SHMT1(1420), dietary folate intake, and preterm and small-for-gestational-age (SGA) birth in a nested case-control study of black and white women. White carriers of SHMT1(1420)T or MTRR(66)A had an increased risk of spontaneous preterm birth (odds ratio [OR] = 1.9, 95% CI 1.1-3.1; OR = 2.0, 95% CI 1.1-3.6 respectively). In black women, there appeared to be an interaction between dietary folate intake and the SHMT1(1420)T variant allele, such that only carriers who also were in the lowest quartile of dietary folate intake had higher risk of spontaneous preterm birth (OR = 2.6, 95% CI 0.8-8.0) and SGA (OR = 2.9, 95% CI 0.9-8.9). Our results suggest the possibility of a direct or indirect role for the SHMT1(1420)T variant in spontaneous preterm or SGA births.