Cannabis use in pregnancy linked to autism risk

18 September 2020

Children whose mothers reported using cannabis during pregnancy have a higher risk of autism, say researchers.

The incidence of autism was four per 1000 person-years among children exposed to cannabis in pregnancy, compared with 2.42 among unexposed children.

The research, published in Nature Medicine, is the largest of its kind ever undertaken, and used data from every birth in Ontario between 2007 and 2012 – before legalisation. About 3000 women (0.6%) reported using cannabis during pregnancy.

Canadian health authorities recommend pregnant women or those breastfeeding avoid cannabis, and warnings appear on packaging.

‘Despite these warnings, there is evidence that more people are using cannabis during pregnancy,’ said Dr Mark Walker, senior author. ‘This is concerning, because we know so little about how cannabis affects pregnant women and their babies.’