(CNN) -- According to a new study published in the journal JAMA Tuesday, more women are using pot, especially those younger in age. Marijuana use was linked to treating morning sickness or heightened anxiety, CNN reports.
From 2009 through 2016, California moms-to-be used more marijuana, from 4.2 percent in 2009 to 7.1 percent in 2016. In teens younger than 18 who were pregnant, use climbed from 12.5 percent to 21. 8 percent. In women aged 18 to 24, use climbed from 9.8 percent to 19 percent.
While the new study involved only certain Californian women, a different study published in January 2017 found pregnant women across the country who reported using marijuana within the last month grew to 3.85 percent in 2014 from 2.37 percent in 2002. The women involved in the study were aged 18 to 44.
According to the Centers for Disease Control and Prevention, marijuana could cause low birth weight and developmental problems for a fetus, though complete health effects remain unclear.
The American Congress of Obstetricians and Gynecologists recommended women "who are pregnant or contemplating pregnancy should be encouraged to discontinue marijuana use." Their recommendations also said that "there are insufficient data to evaluate the effects of marijuana use on infants during lactation and breastfeeding, and in the absence of such data, marijuana use is discouraged."