Researchers observed a sample of pregnant women in California and saw a 3-percent increase in use form 2009 through 2016. For women in the 18 to 24 age bracket, marijuana usage spiked from 12.5 percent to 21.8 percent in that same period.
"Marijuana use in pregnancy may be on the rise in part because the legalization of medical marijuana has made people think of the drug as less unsafe, even during pregnancy", Barbara Yankey, a public health researcher at Georgia State University, told NBC News.
The Journal of the American Medical Association, known as JAMA, published on December 26, a research letter on data analysis that indicates cannabis use is increasing among pregnant women, and particularly for young mothers. According to one survey conducted between 2007 and 2012, 79 percent of women "reported perceiving little to no harm in prenatal [pot] use", the Kaiser team noted.
Worryingly, if women are not reporting their marijuana use in their medical records, their doctors are unable to counsel them about the risks of using marijuana, or what alternative reliefs for symptoms like nausea might be available.
Researchers relied on self-administered questionnaires completed by 279,457 women eight weeks into their pregnancy.
"Think about marijuana use from [the study participants'] perspective, especially in Northern California", said Dr. Robyn Horsager-Boehrer, a professor of obstetrics and gynecology at the University of Texas, who was not involved in the study.
They also say 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".
While the letter does not discuss any potential problems from pot use during pregnancy, the Centers for Disease Control and Prevention (CDC) advises pregnant women to avoid it.
Participating women were asked to answer a questionnaire and go through a drug test to see if they tested positive for marijuana use.
Recreational marijuana use is now legal in eight U.S. states and the District of Columbia. "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".