Women who are overweight during pregnancy have an increased risk of having a child with autism. But genetics, not the obesity per se, may underlie the association, according to a study published 4 June in the International Journal of Epidemiology 1.
The study is the largest to date to point to maternal weight as a factor in autism 2,3.
It found that being overweight during pregnancy does not track with autism when researchers analyze pregnancies in only women who have both affected and unaffected children. The researchers defined ‘overweight’ as having a body mass index (BMI) between 25 and 30.
“When we looked at our data we were actually very, very surprised to see that the association with the maternal BMI had completely gone away,” says lead researcher Renee Gardner, assistant professor of public health sciences at the Karolinska Institute in Sweden. “It was a surprise that really forced a change of perspective.”
More likely, she says, maternal weight is a marker for a genetic contributor to autism.