Days after the American Heart Association released a statement advising against smoking cannabis products, an extensive study, published Monday in the journal Nature, found that women who used marijuana during pregnancy were 1.5 times more likely to have a child with autism.

The study found “an association between maternal cannabis use in pregnancy and the incidence of autism spectrum disorder in the offspring.”.

It did not capture the amount and type of marijuana the women used or when during the pregnancy or how often women used it.

The study does not definitively prove that marijuana use during pregnancy causes autism, only that there is an association between the two factors.

A National Institutes of Health study back in 2013 found that pregnant women who use marijuana have a 2.3 times greater risk of stillbirth.

Last Wednesday, in a statement published in the AHA journal Circulation, the American Heart Association said it “recommends that people not smoke or vape any substance, including cannabis products, because of the potential harm to the heart, lungs and blood vessels.” Clinical pharmacologist Robert Page II, who chaired the medical writing group for the statement, wrote that using marijuana has “the potential to interfere with prescribed medications” and “trigger cardiovascular conditions or events, such as heart attacks and strokes.” Page added that if individuals choose to use cannabis products, “the oral and topical forms, for which doses can be measured, may reduce some of the potential harms.”