According to the results of a Norwegian observational study, women who took folic acid supplements in the first two months of pregnancy were less likely to have children with severe language delays.

The authors note that randomised controlled trials (RCTs) have shown peri-conceptual folic acid supplementation to reduce the risk of neural tube defects; however to their knowledge none have followed up the participants to investigate whether such supplementation has any effects on neurodevelopment following birth.  They therefore used data from the prospective Norwegian Mother and Child Cohort Study to investigate whether maternal use of folic acid supplements was associated with a reduced risk of severe language delay in their children at age 3 years.

The Norwegian Mother and Child Cohort Study is a prospective pregnancy cohort that recruited 108,841 pregnant women between 1999 and December 2008 through a postal invitation (participation rate of 38.5%).  Data collection during pregnancy and at birth included self-reported questionnaires and biological samples from the mother, father and child; questionnaires were also sent to the entire sample up to the age of 3 years.  The current analysis included data released in 2010 for 44,220 children born before 2008, for whom the age 3 questionnaire had been returned.  After exclusion of twins/triplet, those born early or with low birth weight, and those with hearing problems, the main analysis included 38,954 children.

The exposure of interest was maternal use of folic acid supplements within the interval from 4 weeks before to 8 weeks after conception, and the main outcome measure was children's language competency at age 3 years, measured by maternal report on a 6-point ordinal language grammar scale.  Children with minimal expressive language (only 1-word or unintelligible utterances) were rated as having severe language delay.

A total of 204 children (0.5%) had severe language delay, including 81 in the group whose mothers took no dietary supplements in the specified exposure interval (reference group; n=9052 [0.9%]).  Compared to the reference group, use of folic acid only (n=7127 [18.9%]) was associated with a reduced risk of severe language delay (seen in 28 children [0.4%]; OR 0.55; 95% CI 0.35-0.86), as was use of folic acid in combination with other supplements (n=19,005 [50.5%]; severe language delay in 73 children [0.4%]; OR, 0.55; 95% CI, 0.39-0.78).  The use of other supplements without folic acid (n=2480 [6.6%]) was not associated with any reduced risk of severe language delay in the offspring (22 children [0.9%]; OR 1.04; 95% CI 0.62-1.74).  The authors note that there was no association between maternal use of folic acid supplements and significant delay in gross motor skills at age 3 years.

The authors discuss the limitations of their study, including the possibility of confounding and selection bias, and caution that causality cannot be established.  If however future studies demonstrate this relationship to be causal, it would have “important implications for understanding the biological processes underlying disrupted neurodevelopment, for the prevention of neurodevelopmental disorders, and for policies of folic acid supplementation for women of reproductive age.”