The number of pregnant women using marijuana has risen in California since the state relaxed its drug laws, a new study has found. The increase was especially sharp among young women, rising from 12.5 percent to nearly 22 percent for mothers to be under the age of 24, in the years between 2009 and 2016.
It’s not exactly news that women use marijuana to cope with symptoms of pregnancy, from morning sickness to the anxiety that comes with expecting a child. In fact, pregnant women have used marijuana—and marijuana products like topicals—for millennia.
The report does not directly draw a connection between the increase and laxer marijuana laws. But the period covered coincides with California steadily loosening penalties for marijuana use, mirroring a national trend. But the study’s author’s wrote that “continued monitoring of trends, exposure timing, and offspring outcomes is important as marijuana potency rises in an increasingly permissive legal landscape.”
The women were screened for marijuana use at approximately eight weeks’ gestation. The researchers found that the prevalence of marijuana use, based on self-reports or toxicology results, soared among all age groups, but the biggest rise was among those 24 and younger.
“We were concerned to find that the prevalence of marijuana use in pregnancy is increasing more quickly among younger females, aged 24 and younger, and to see the high prevalence of use in this age group” Kelly Young-Wolff, the study’s lead author
For other age groups, the researchers found that marijuana use rose from 3.4% to 5.1% among women 25 to 34 and from 2.1% to 3.3% among women older than 34.
Pregnancy in adolescents has been linked to increases in behaviors such as drinking and marijuana use, and pot use could have a disproportionate effect on the increase seen among teens in the study because the adolescent participant group had fewer members than the adult groups.
For instance, moms-to-be younger than 18 years were only 1.4% of the overall sample in the study, but 18 to 24 were 15.8%, 25 to 34 were 61.6%, and older than 34 were 21.2%.
Additionally, “we were unable to distinguish prenatal use before versus after women realized they were pregnant,” Young-Wolff wrote.
The findings also were limited to data on pregnant women within one health care system in a limited geographic area of California.
All in all, “the paper is not surprising, and the findings of a rise in marijuana use during pregnancy is consistent with recent attention to marijuana and legalization in various states,” said Dr. Haywood Brown, professor of obstetrics and gynecology at Duke University School of Medicine, who was not involved in the new study.
An advantage of the study, he added, was that women not only self-reported marijuana use but also were screened for marijuana – and he thinks the study findings are age-related, as the largest increase in marijuana use was among adolescents and young adults.
As the study showed the highest increase in marijuana use among women 24 and younger, that age group might hold clues as to why there has been an overall increase, said Dr. Robyn Horsager-Boehrer, professor and chief of obstetrics and gynecology at the University of Texas Southwestern’s William P. Clements Jr. University Hospital.
“Think about marijuana use from their perspective, especially in Northern California. California legalized medical marijuana use in 1996, so they have grown up with the idea of it not only not being illegal but being a medical therapy,” said Horsager-Boehrer, who was not involved in the study.
“With the proximity to Oregon and Washington, they also have experience with any use being legal,” she said. “So I think the idea that use is rising is just because of the greater legal exposure to marijuana that women have today versus 20 years ago.”
Young-Wolff noted in her email that the study itself did not investigate reasons for the rise in marijuana use among pregnant women.
These findings about pregnant women are certain to cause concern. After all, there has been some research about how consuming marijuana while pregnant can be detrimental to infants, resulting in a low birth weight as well as developmental issues. But there’s also been research that says otherwise. Arguably the most comprehensive study on cannabis use during pregnancy was done by Dr. Melanie Dreher in the 80s. Surprisingly, it found that infants who were exposed to cannabis in the womb scored higher on their reflex tests than infants who weren’t. Dreher tested the children again at ages four and five and found no changes in IQ or behavioral performance as a result of cannabis use. The second study, conducted by Dr. Shayna Conner, came about in 2016. She found that marijuana did not increase the risk of adverse health outcomes, but that alcohol and tobacco did.