Kaiser Permanente study finds that the risk of autism — while low — is greater for children exposed to severe morning sickness early in pregnancy

Children whose mothers had hyperemesis gravidarum — a severe form of a morning sickness — during pregnancy were 53% more likely to be diagnosed with autism spectrum disorder, according to Kaiser Permanente research published in the American Journal of Perinatology.

“This study is important because it suggests that children born to women with hyperemesis may be at an increased risk of autism,” said lead study author Darios Getahun, MD, PhD, of Kaiser Permanente Southern California Department of Research and Evaluation. “Awareness of this association may create the opportunity for earlier diagnosis and intervention in children at risk of autism.”

Hyperemesis gravidarum occurs in less than 5% of pregnancies. Affected women experience intense nausea and are unable to keep down food and fluids. This can lead to dangerous dehydration and inadequate nutrition during pregnancy.

To determine the extent of the association between hyperemesis gravidarum and autism spectrum disorder, researchers reviewed electronic health records of nearly 500,000 pregnant women and their children born between 1991 and 2014 at Kaiser Permanente in Southern California. They compared children whose mothers had a diagnosis of hyperemesis gravidarum during pregnancy to those whose mothers did not.

Other findings from the research included:

• Exposure to hyperemesis gravidarum was associated with increased risk of autism when hyperemesis gravidarum was diagnosed during the first and second trimesters of pregnancy, but not when it was diagnosed only in the third trimester.
• Exposure to hyperemesis gravidarum was associated with risk of autism regardless of the severity of the mother’s hyperemesis gravidarum.
• The association between hyperemesis gravidarum and autism spectrum disorder was stronger in girls than boys and among whites and Hispanics than among blacks and Pacific Islanders.
• The medications used to treat hyperemesis gravidarum did not appear to be related to autism risk.

The results are consistent with the hypothesis that women experiencing hyperemesis gravidarum have poor nutritional intake, which may, in turn lead to potential long-term neurodevelopment impairment in their children. The study cannot, however, rule out other possible explanations, such as perinatal exposures to some medications and maternal smoking.