A government survey shows pot use in pregnancy has doubled among U.S. women and is most common during the first trimester.
Overall, 7% of pregnant women said they used marijuana in the past month. That's from a nationally representative health survey in 2016-17 and compares with a little over 3% in 2002-03.
First trimester use went from almost 6% to 12%.
Some studies have linked marijuana use during pregnancy with increased chances of premature birth and low birth weight.
Dr. Nora Volkow, director of the National Institute on Drug Abuse, said it's not known how harmful marijuana use is during pregnancy and it isn't worth the risk.
The study was presented at a medical meeting Tuesday and published online in the Journal of the American Medical Association.