Research has established that taking folic acid supplements during pregnancy reduces the risk of bearing a child with neural tube defects, but little is known about the relationship between prenatal folic acid and neurodevelopment after birth. A collaborative study between investigators at the Norwegian Institute of Public Health and Columbia University’s Mailman School of Public Health has now reported that mothers who took folic acid supplements from 4 weeks before to 8 weeks after conception reported a significantly lower prevalence of severe language delay in their children at age 3. The study was based in a unique Norwegian pregnancy cohort often referred to as “MoBa”.
The full study findings are published online in the October 12 issue of JAMA.
The current analysis included 19,956 boys and 18,998 girls. Of these children, 204 (0.5%) were rated as having severe language delay, defined as minimal expressive language, only 1-word or unintelligible utterances. Among women who took folic acid supplements in early pregnancy, the reported prevalence of such delay was 0.4%, but among the approximately 9,000 children whose mothers took no folic acid, the delay was more than twice as common: 0.9% (81 children).
Across the entire sample, severe language delays were four times more common in boys than girls, as is typically the case.
“Unlike the United States, Norway does not fortify foods with folic acid—a fact that increases the contrast between women who do and do not take folic acid supplements and makes Norway a good place to study this effect,” noted lead author Christine Roth, Clin.Psy.D., MSc, of the Division of Mental Health at the Norwegian Institute of Public Health, Oslo and a visiting researcher at the Mailman School.
“If in future research this relationship were shown 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,” said senior author Dr. Ezra Susser, director of the Imprints Center for Genetic and Environmental Life Course Studies, of the Mailman School of Public Health and the New York State Psychiatric Institute.
Pregnant women were recruited for the study beginning in 1999, and data were included on children born before 2008 whose mothers returned the 3-year follow-up questionnaire by June 2010. The primary outcome measured for the study was children's language competency at age 3 years as gauged by maternal report on a 6-point ordinal language grammar scale.
Researchers also looked at gross motor skills at age 3 and found no relationship between significant motor delays and prenatal folic acid. “This provides some reassurance that there is not confounding by an unmeasured factor,” the authors observed. “Such a factor might be expected to relate to both language and motor delay.”
The study, if corroborated by further research, could help further scientific understanding of the biology of language development. The researchers plan to pursue this question further with stringent tests of whether the relationship is causal, studies of the hypothesized mechanisms, and detailed follow-ups of the children at age 5.
The study was funded by the Norwegian Research Council.