The number of women who use marijuana while pregnant is increasing, especially among teenage and young pregnant mothers, a new report in the Journal of the American Medical Association (JAMA) suggested.

Researchers examined data from 279,457 pregnant women who were patients at the Kaiser Permanente Northern California health care system from 2009 to 2016, and participated in a self-administered questionnaire on marijuana use since pregnancy, as well as a cannabis toxicology test during their standard prenatal care visits.

Among pregnant mothers who were younger than 18, researchers said the prevalence of prenatal marijuana use based on the self-report or toxicology test increased from 12.5 percent to 21.8 percent from 2009 to 2016.

For pregnant mothers between the ages of 18 and 24, the prevalence of prenatal marijuana use increased from 9.8 percent to 19 percent from 2009 to 2016, researchers found.

In addition, for women aged 25 to 34, the increase was from 3.4 percent to 5.1 percent, and for women older than 34, the increase was from 2.1 percent to 3.3 percent from 2009 to 2016.

The JAMA research letter added that while medical marijuana was legalized in 1996 in California, "prenatal use may further escalate in 2018 when recreational marijuana is available legally."

The U.S. Centers for Disease Control and Prevention (CDC) stated on its website that some pregnant women may have "turned to using marijuana to ease nausea or other pregnancy