Unsurprisingly, the number of people between the ages of 18 and 25 who smoke marijuana is increasing greatly, mainly due to recreational legalization. But it turns out a cannabis use is growing in a demographic you might not expect: pregnant women.

A new study from the Journal of the American Medical Association that the number of pregnant women who use marijuana has grown in the last eight years. The study examined 30,000 women in California enrolled in the state's largest HMO. They looked at how the women responded in a questionnaire given at their eight week prenatal examine. According to the study, the number of women who either self-reported to using marijuana or tested positive for it increased from 4.2 percent to 7.1 percent between 2009 and 2016. The numbers were higher among younger women, with 22 percent of pregnant teenagers testing positive for marijuana, and 19 percent for women between 18 and 24. 

The question is how bad is this information. Unfortunately, there isn't very much medical evidence on how marijuana use affects pregnancy. Some studies have found a possible link between cannabis use and low birth weight and other health problems. But a review of 31 studies on marijuana and pregnancy conducted last year found no clear link between the cannabis and health problems in babies. Still, the authors of that review said they still would advise against pregnant women using marijuana.

That viewpoint isn't shared by actual women. The American Medical Association in their recent study said that 80 percent of women believe using cannabis while pregnant is risk-free. And there honestly isn't much scientific evidence to prove them wrong.

So while marijuana should be avoided while pregnant, we also need more medical evidence to determine what the actual risks are of doing so. We don't stick the Surgeon General's Warning on cigarettes because they might harm unborn babies. We do so because we know how it does. We need the same information for marijuana as well.

(h/t Gizmodo)