Folic acid supplementation may be beneficial in the later stages of pregnancy

Pregnant women could benefit from folic acid supplementation to maintain an optimal folate level during pregnancy and to prevent the decline in serum folate and elevation in homocysteine concentrations that otherwise can occur in the later stages of pregnancy.

Maternal folic acid supplementation has been believed to prevent neural tube defects, subclinical folate deficiency as well as megaloblastic anemia before and during early pregnancy. In a normal pregnancy, maternal folate status will decrease in an effort to support fetal, placental and maternal tissue growth. Moreover, an increased rate of folate catabolism may also lead to a decreased maternal folate status. Folate is required for DNA synthesis and methylation processes, including the remethylation of homocysteine to methionine, which is a critical factor in regulating plasma homocysteine concentration. Elevated plasma homocysteine levels (also known as hyperhomocysteinemia) have been linked with various pregnancy complications such as neural tube defects, preeclampsia, low birth weight, recurrent early pregnancy, placenta abruption and intrauterine growth retardation. Despite this, no folic acid recommendations exist after the 12th week of pregnancy. Therefore, this study was conducted to investigate if continued folic acid supplementation beyond the first trimester of pregnancy was beneficial for maternal folate and homocysteine levels and related newborn outcomes.

For this study, healthy women with singleton pregnancies, aged 18-35 y, were assigned randomly at the start of trimester 2 to receive either 400 μg of folic acid each day or a placebo capsule until the end of pregnancy. There were 119 women (60 women in the placebo group; 59 women in the treatment group) who completed the trial. From the 14th to 34th gestational weeks, posttreatment concentrations of serum folate (P < 0.001) and red blood cell folate (P < 0.001) were lower; plasma homocysteine concentrations were higher in the placebo than folic acid-treated groups. From gestational weeks 14-36, mean serum folate declined in unsupplemented women by 56% (P < 0.001); red blood cell folate decreased by 21%, whereas plasma homocysteine increased by 1 μmol/L (P < 0.001). However, folic acid supplementation prevented the changes in serum folate, plasma homocysteine and significantly increased red blood cell folate concentrations (P < 0.001). In infants of mothers supplemented with folic acid, a comparison of cord blood B vitamin concentrations between treatment groups showed higher serum and red blood cell folate concentrations, whereas neither homocysteine nor vitamin B-12 concentrations were different.

The findings suggest that pregnant women could benefit from folic acid supplementation to maintain an optimal folate level during pregnancy and to prevent the decline in serum folate and elevation in homocysteine concentrations that otherwise can occur in the later stages of pregnancy.

References

  1. McNulty, B., et al., Impact of continuing folic acid after the first trimester of pregnancy: findings of a randomized trial of Folic Acid Supplementation in the Second and Third Trimesters. Am J Clin Nutr, 2013. 98(1): p. 92-8.