This study examined whether prenatal vitamin use by mothers was associated with autism spectrum disorder (ASD) recurrence in high-risk families. The study included 241 children who were selected because a sibling was diagnosed with ASD. Mothers reported their use of prenatal vitamins during pregnancy.
While most mothers reported taking prenatal vitamins while pregnant, only 87 (36 percent) mothers met the recommendations to take prenatal vitamins in the six months before pregnancy. Researchers report that children whose mothers had taken prenatal vitamins during the first month of pregnancy appeared less likely to be diagnosed with ASD when compared with children whose mothers hadn't taken prenatal vitamins during that time. The proportion of children with ASD among mothers who took prenatal vitamins in the first month of pregnancy was 14.1 percent (18 children) compared with 32.7 percent (37 children) among those whose mothers didn't take prenatal vitamins during that time. 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. This study is important because there have been conflicting studies about whether maternal prenatal vitamin use is associated with a lower risk of ASD. More research is needed to confirm the associations observed in this study.