Folic acid during pregnancy: methylation differences in children, with no established clinical significance

A review focused on a specific region of DNA

Folates contribute to one-carbon metabolism, which is involved in methylation reactions. This function provides a biological rationale for studying links between maternal folate exposure and DNA methylation in children. On its own, it does not demonstrate an effect on their health.

The researchers focused on the IGF2-H19 locus, which is involved in fetal growth and developmental programming. Their review brings together fifteen publications from nine countries: two randomized trials, two cross-sectional studies and eleven cohort studies.

The studies examined folate or folic acid intake during pregnancy and methylation in various pregnancy-related tissues. The available abstract provides neither the total number of participants nor a common follow-up period.

Associations differ by region and tissue

Folic acid supplementation showed the most consistent associations in the H19 imprinting control region. Some cord blood analyses reported an association with lower methylation. This finding therefore did not apply uniformly across all tissues or regions studied.

For the IGF2 DMR2 region, findings varied between studies. Associations with blood folate markers were generally weak and tissue-dependent. Analyses of dietary folate intake generally found no association.

These differences mean that dietary intake, folic acid supplementation and blood folate concentrations cannot be treated as equivalent.

A methylation difference is not a clinical outcome

Lower or higher methylation does not automatically mean better or worse health. The reported conclusion concerns modest, localized molecular differences whose biological significance remains uncertain.

Study quality also limits interpretation: no observational study was judged to have a low overall risk of bias. The assessment of the two randomized trials also raised some concerns.

This review alone therefore does not justify changing supplementation during pregnancy. It mainly documents an unresolved question about the relationships between maternal folate exposure and methylation in children.

What we can take away

The observed signal is molecular, modest and context-dependent. It demonstrates neither a clinical benefit nor a clinical risk from maternal folic acid supplementation.