Pregnancy is hard. It ages you, squashes your organs in bizarre ways, and the only consolation is an improved ability to scam extra food from zookeepers. But perhaps one of the most famous side-effects, affecting more than half of expectant mothers, is morning sickness.

Now, morning sickness is a tricky devil. Despite its pervasiveness, it turns out we still don't really know what causes it, or how to get rid of it. Attempts to medicate it away in the past have had notoriously tragic results, and – aside from some vitamin tablets and antihistamines if it gets really bad – modern women are often left turning to traditional or folklore remedies to soothe their symptoms.

So perhaps it's no wonder, then, that women might be increasingly resorting to more extreme methods to treat their nausea. A new study published in the Journal of the American Medical Association suggests a worrying upsurge in one home remedy in particular: cannabis.

The fact that more women are using marijuana while pregnant is not new – a study last year revealed that the number of women self-reporting cannabis use during pregnancy had increased by 75 percent between 2002 and 2014. The new research, which follows on from those findings and looked at 220,000 pregnancies, wanted to find out why that was.

"This is the largest study to date of nausea and vomiting in pregnancy and prenatal marijuana use," lead author Kelly Young-Wolff explained in a press release. "Our findings add important evidence to a small but growing body of research suggesting that some pregnant women may use marijuana to self-medicate morning sickness."

Although the rates of marijuana use in pregnancy were only a little over 1 in 20 – a prevalence rate half that of alcohol and two-thirds of smoking while pregnant – the study found that women with mild nausea and vomiting were more than twice as likely to report using the drug when compared to women without morning sickness. Among women with severe symptoms, that increased to nearly four times as likely.

Of course, correlation is not causation, and the study notably refrains from drawing too much of a conclusion from their results. 

"The results are consistent with the hypothesis that women use marijuana to self-medicate for nausea and vomiting in pregnancy," notes the press release, "but the study cannot rule out other possible explanations, such as whether marijuana use contributes to nausea and vomiting in pregnancy, or whether clinicians diagnose nausea and vomiting in pregnancy more frequently among women who report using marijuana to treat it."

Cannabis use is – to say the least – not medically advised during pregnancy. A 2016 meta-analysis linked the drug to low infant birth weight, maternal anemia, and, shockingly, an increased likelihood of the newborn spending time in intensive care. A large majority of women in the 2017 study were unaware of these risks, however, with 79 percent saying they felt there was "little to no harm" associated with cannabis use during pregnancy. 

"We hope our study can help alert clinicians to the fact that women with nausea and vomiting in pregnancy are more likely to use marijuana,” senior author Nancy Goler said. "Pregnant women need to be screened and given the information about the possible negative effects, while also receiving medically recommended treatment options."