Maternal use of folic acid supplements has been inconsistently associated with reduced risk for autism spectrum disorder (ASD) in the child. This study, published in JAMA Psychiatry, examined whether prenatal vitamin use by mothers was associated with autism spectrum disorder (ASD) recurrence in high-risk families.
This prospective cohort study analyzed data from a sample of children (n = 332) and their mothers (n = 305) enrolled in the 
MARBLES (Markers of Autism Risk in Babies: Learning Early Signs) study. Participants in the MARBLES study were recruited at the MIND Institute of the University of California, Davis and were primarily 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 December 1, 2006, and June 30, 2015, and completed a final clinical assessment within 6 months of their third birthday. Prenatal vitamin use during pregnancy was reported by mothers during telephone interviews. Data analysis for this study was conducted from January 1, 2017, to December 3, 2018.
The study reported the following results:
- Most mothers (231 [95.9%]) reported taking prenatal vitamins during pregnancy, but only 87 mothers (36.1%) met the recommendations to take prenatal vitamins in the 6 months before pregnancy.
- 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.
- Children in the former maternal prenatal vitamin group also had statistically significantly lower autism symptom severity (adjusted estimated difference, –0.60; 95% CI, –0.97 to –0.23) and higher cognitive scores (adjusted estimated difference, 7.1; 95% CI, 1.2-13.1).
This study is important because there have been conflicting studies about whether maternal prenatal vitamin use is associated with a lower risk of ASD. One limitation is that this study was observational, which means there may have been differences between the two groups that weren’t accounted for during the analysis, even though the investigators accounted for many factors. Another limitation is the study’s relatively small sample size. More research is needed to confirm the associations observed in this study.
Conclusion /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.
Source: Rebecca J. Schmidt, Ph.D., et al. Association of Maternal Prenatal Vitamin Use With Risk for Autism Spectrum Disorder Recurrence in Young Siblings, JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.3901
