Younger siblings of children with autism spectrum disorder (ASD) whose mothers took prenatal vitamins were less than half as likely to be diagnosed with ASD themselves, compared with those whose mothers did not take prenatal vitamins, research has shown. The authors of the small study*, published in JAMA Psychiatry, pointed out that their study was purely observational and said additional research is needed to confirm their results, to further investigate specific nutrients, and to inform public health recommendations for ASD prevention.
In previous research, maternal use of folic acid supplements has been inconsistently associated with the child having a reduced risk for ASD, but no study to date had examined this association in the context of ASD recurrence in high-risk families. This research team, from the University of California, designed a prospective cohort study to examine the association between maternal prenatal vitamin use and ASD recurrence risk in younger siblings of children with ASD.
Participants were a sample of 332 children and their mothers (305) enrolled in the MARBLES (Markers of Autism Risk in Babies: Learning Early Signs) study, who had been recruited at the MIND Institute of the University of California, Davis, and came largely from families receiving services for children with ASD in the California Department of Developmental Services. In this sample, the younger siblings at high risk for ASD were born between 1st December 2006 and 30th June 2015, and completed a final clinical assessment within six months of their third birthday. The mothers reported, via telephone interview, their use of prenatal vitamins during pregnancy. The final sample for analysis included 241 younger siblings, (140 boys and 101 girls), with a mean age of 36.5 months.
The researchers found that although most (95.9%) of the mothers said they had taken prenatal vitamins during pregnancy, only 87 mothers (36.1%) met the recommendations to take prenatal vitamins in the six months before pregnancy.
They reported that the prevalence of ASD was 14.1% (18) in children whose mothers took prenatal vitamins in the first month of pregnancy compared with 32.7% (37) in children whose mothers did not take prenatal vitamins during that time. Those children whose mothers said they had taken prenatal vitamins during the first month of pregnancy were significantly less likely to receive an ASD diagnosis (adjusted relative risk, RR 0.50) than the children whose mothers had not taken prenatal vitamins; but there was no statistically significant impact on the risk of a non-typical development 36-month outcome (RR 1.14). Children in the former maternal prenatal vitamin group also had statistically significantly lower autism symptom severity and higher cognitive scores.
They concluded: “Maternal prenatal vitamin intake during the first month of pregnancy may reduce ASD recurrence in siblings of children with ASD in high-risk families. Additional research is needed to confirm these results; to investigate dose thresholds, contributing nutrients, and biologic mechanisms of prenatal vitamins; and to inform public health recommendations for ASD prevention in affected families.”
*Schmidt RJ, Iosif A, Guerrero Angel E, Ozonoff S. Association of maternal prenatal vitamin use with risk for autism spectrum disorder recurrence in young siblings. JAMA Psychiatry. Published online February 27, 2019. doi:10.1001/jamapsychiatry.2018.3901.