Autism continues to puzzle scientists, but a recent study from researchers at Johns Hopkins University has shed new light into what may cause the mental disorder. According to a Reuters report, scientists have shown that women who are both obese and suffer from diabetes are at least four times as likely to give birth to a child with autism than a mother of good health.

Mothers who were obese were only shown to have twice the likelihood of giving birth to a child with autism when compared with mothers of normal weight. The study was published in the journal Pediatrics.

According to Dr. Xiaobin Wang, a public health and pediatrics researcher at JHU, the rate of autism spectrum disorder is relatively low in the United States population. Despite the low incidence of the disease, it can have huge impacts on families and society at large.

ASD affects roughly one in 68 children in the U.S., including autism, Asperger syndrome and a wide range of other developmental disorders. Affecting roughly 1.5 percent of American children, researchers have long sought a better understanding of the underlying causes.

So far, scientists have spent a great deal of time examining the effects of maternal health on a child’s likelihood of developing autism. The recent study suggested that roughly 3 percent of babies born to obese mothers are autistic, and almost 6 percent of babies born to mothers who were both obese and had diabetes.

Scientists examined data on 2,734 mothers and their babies, collected at the Boston Medical Center between 1998 and 2014. The majority of the children in the sample, 64 percent, were not diagnosed with ASD or similar developmental disorders. 102 of the children in the sample were diagnosed with ASD.

Scientists aren’t sure exactly why a mother’s weight affects the risk of ASD diagnoses, but they believe it could have something to do with the risk of inflammation or the different concentrations of nutrients and hormones in people who are obese or suffer from diabetes. More studies will need to be done in order to further establish a link between obesity, diabetes and autism.

A press release from Johns Hopkins University describing the details of the recent study can be found here.