CHICAGO – In a study that included approximately 85,000 Norwegian children, maternal use of supplemental folic acid from 4 weeks before to 8 weeks after the start of pregnancy was associated with a lower risk of autistic disorder in children, according to a study appearing in the February 13 issue of JAMA.
“Supplementation with folic acid around the time of conception reduces the risk of neural tube defects in children. This protective effect has led to mandatory fortification of flour with folic acid in several countries, and it is generally recommended that women planning to become pregnant take a daily supplement of folic acid starting 1 month before conception,” according to background information in the article. It has not been determined whether prenatal folic acid supplements protect against other neurodevelopmental disorders.
Pal Surén, M.D., M.P.H., of the Norwegian Institute of Public Health, Oslo, and colleagues investigated the association between the use of maternal folic acid supplements before and in early pregnancy and the subsequent risk of autism spectrum disorders (ASDs) (autistic disorder, Asperger syndrome, pervasive developmental disorder-not otherwise specified [PDD-NOS]) in children. The study sample of 85,176 children was derived from the population-based, prospective Norwegian Mother and Child Cohort Study (MoBa). The children were born in 2002-2008; by the end of follow-up on March 31, 2012, the age range was 3.3 through 10.2 years (average age, 6.4 years). The exposure of primary interest was use of folic acid from 4 weeks before to 8 weeks after the start of pregnancy, defined as the first day of the last menstrual period before conception. Analyses were adjusted for maternal education level, year of birth, and parity (the number of live-born children a woman has delivered).
A total of 270 children (0.32 percent) in the study sample have been diagnosed with ASDs: 114 (0.13 percent) with autistic disorder, 56 (0.07 percent) with Asperger syndrome, and 100 (0.12 percent) with PDD-NOS. The researchers found that there was an inverse association between folic acid use and subsequent risk of autistic disorder. Autistic disorder was present in 0.10 percent (64/61,042) of children whose mothers took folic acid, compared with 0.21 percent (50/24,134) in children whose mothers did not take folic acid, representing a 39 percent lower odds of autistic disorder in children of folic acid users.
Characteristics of women who used folic acid within the exposure interval included being more likely to have college- or university-level education, to have planned the pregnancy, to be nonsmokers, to have a pre-pregnancy body mass index below 25, and to be first-time mothers.
“No association was found with Asperger syndrome or PDD-NOS, but power was limited. Similar analyses for prenatal fish oil supplements showed no such association with autistic disorder, even though fish oil use was associated with the same maternal characteristics as folic acid use,” the authors write.
The researchers note that the inverse association found for folic acid use in early pregnancy was absent for folic acid use in mid pregnancy.
“Our main finding was that maternal use of folic acid supplements around the time of conception was associated with a lower risk of autistic disorder. This finding does not establish a causal relation between folic acid use and autistic disorder but provides a rationale for replicating the analyses in other study samples and further investigating genetic factors and other biological mechanisms that may explain the inverse association,” the authors conclude.