Fewer woman are opting to drink and smoke cigarettes during pregnancy than in previous years, but more are choosing to use marijuana, according to new research.
Published Monday in JAMA Pediatrics, the survey focused on pregnant women between 2002 and 2016. It found about 10 percent of women smoked cigarettes while pregnant in 2016, compared to 17.5 percent 14 years before. Over the same timeframe, alcohol use during pregnancy dropped from 10 percent of women to 8.5 percent. And while cannabis is still the least popular substance of the three to use during pregnancy, it was also the only one that increased. It rose from 3 percent of pregnant women to almost 5 percent by 2016.
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The data came from about 12,000 women who responded to the National Survey of Drug Use and Health. About 3,500 of respondents said they were in their first trimester, when the fetus is most vulnerable.
The paper itself doesn’t address what’s causing these trends, but they align with general patterns of behavior among U.S. adults. For example, marijuana laws have become significantly laxer in recent years, and fewer people smoke cigarettes than ever before. According to TIME, most states have legalized medical marijuana, and recreational pot is permitted in nine. The popularity of alcohol has remained fairly steady.
There’s less research about the effects of marijuana use during pregnancy than data on cigarettes and alcohol (though there’s no definitive conclusion on how many drinks during pregnancy are too many), but experts generally agree that no amount of pot is safe.
For example, Dr. Mary Jane Minkin, an OB-GYN from Yale University and member of PEOPLE’s Health Squad, “strongly discourages women from using marijuana in any form during pregnancy.”
“Even if the mom smokes just one time, there are studies showing that it crosses the placenta. That causes the concentration of THC in the baby to be about 10 percent of that in the mom. And with repeated uses, the amount goes up,” Dr. Minkin tells PEOPLE. “The other problem is that THC binds well to fats, in cell membranes, and can achieve a significant level not only in the mom’s brain, but also in the fetal brain.”
Dr. Minkin cites the Oct. 2017 opinion from the American College of Obstetricians and Gynecologists [of which she is a member], which reviewed over 40 studies on marijuana use during pregnancy.
“The studies didn’t find many cases of physical defects, like heart defects, with marijuana use, but there are plenty of studies showing that it can effect what is called impaired neurodevelopment and cognitive development — thinking, behavior and some visual problems,” she adds.
For moms who considering marijuana to combat morning sickness, Dr. Minkin says there are “a lot of other, safer options available … There is even some data on good old vitamin B6, which helps some women with nausea during pregnancy. So please, if you are having nausea, do check in with your midwife or obstetrician.”
Dr. Minkin also advises against using marijuana while breastfeeding because some THC can pass into the milk.