The risk of autism may be reduced for children whose mothers use multivitamins during pregnancy. This is the finding of new research published in The BMJ.
Study co-author Brian K. Lee, of the Dornsife School of Public Health at Drexel University in Philadelphia, PA, and colleagues say that their study is only observational, but that the findings suggest that prenatal vitamin use for autism prevention should be further investigated.
Autism - which is also known as autism spectrum disorder (ASD) - refers to a number of conditions affecting development, resulting in problems with social skills, communication, and behavior. Individuals with autism may also have intellectual disabilities, such as problems with thinking and learning.
According to the Centers for Disease Control and Prevention (CDC), around 1 in 68 children in the United States are living with autism, up from 1 in 150 in 2002.
A number of studies have suggested that a mother's diet during pregnancy may influence the risk of autism in offspring. A study published in 2013, for example, suggested that women who had higher intakes of omega-3 and omega-6 fatty acids during pregnancy were around a third less likely to have children with autism.
The new study from Lee and team builds on such results, after finding that multivitamin use during pregnancy may be linked to a reduced risk of autism in children.
Multivitamins and autism risk
The research involved 273,107 mother and child pairs identified through a population register in Sweden. The children were born between 1996 and 2007 and they were followed up until 2011, when they were aged between 4 and 15 years.
Mothers' supplement use at their first antenatal visit was assessed, and the pairs were allocated to one of six groups as a result: iron supplements only; folic acid supplements only; iron and folic acid supplements; multivitamins only; multivitamins with iron; and multivitamins with folic acid.
Data on autism diagnosis among offspring were gathered using computerized health registers in Sweden.
The researchers found that children born to mothers who used multivitamins during pregnancy - "with or without additional iron or folic acid" - were less likely to have autism with intellectual disability, compared with mothers who did not use these supplements.
The team notes that there was no consistent link between the use of folic acid, iron supplements, or both during pregnancy and a lower risk of autism among offspring.
Further investigation warranted
Because this study is purely observational, the researchers say that they are unable to prove cause and effect between multivitamin use in pregnancy and reduced autism risk among children.
"Given the current understanding and strength of evidence supporting the importance of nutritional supplementation during pregnancy," they say, "these results on their own should not change current practice."
The researchers also point to some study limitations. For example, they were unable to assess any changes to supplement use among mothers after their first antenatal visit. "It is possible that the reported supplement was not taken, or a supplement was taken but not reported," they note.
Still, the team believes that its results warrant further investigation. The authors conclude:
"Maternal multivitamin supplementation during pregnancy may be inversely associated with ASD with intellectual disability in offspring. Further scrutiny of maternal nutrition and its role in the cause of autism is recommended."