Fewer women are smoking cigarettes and drinking alcohol during pregnancy, but more are using marijuana.
Those are the results of responses to a survey by the National Survey of Drug Use and Health.
A research letter published in JAMA Pediatrics says Between 2002 and 2016, the percentage of pregnant women who reported smoking cigarettes while expecting fell significantly: from 17.5% to about 10%.
Alcohol use fell from nearly 10% to about 8.5%.
But cannabis use among pregnant women - while still relatively rare - is on the rise, increasing from almost 3% of pregnant women to almost 5%.
About 12,000 pregnant women ages 18 to 44 responded to the survey between 2002 and 2016; roughly 3,500 of these women were in their first trimester of pregnancy, a critical time for fetal development.
While the new paper did not assess the reasons behind substance use trends, the uptick in cannabis use likely has to do with relaxed marijuana laws across the country.
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