Beginning in late 2020, all cannabis products sold legally in the state of California will be required to contain a new warning label stating that cannabis “may be harmful” for women who are breastfeeding or pregnant, as well as for the women’s developing fetuses and babies.

Scientists with the California’s Office of Environmental Health Hazard Assessment (OEHHA) voted on Dec. 11 to enact this law. This places cannabis smoke and THC on California’s list of reproductive toxicants under the Safe Drinking Water and Toxic Enforcement Act of 1989, also known as Proposition 65. 


The vote was carried out by a panel of nine scientists on OEHHA’s Developmental and Reproductive Toxicant Identification Committee. The panel spent weeks reviewing evidence and concluded that marijuana smoke and THC, one of the plant’s most active ingredients, cause harm to both pregnant women and their developing fetuses, Tracy Woodruff, a member of the committee and a professor at the University of California, San Francisco, said to NPR and WBUR’s Here & Now.

“We reviewed probably several hundred studies,” Woodruff said. “We were focused on the effects of exposure to cannabinoid smoke and THC on development, so development of the fetus.” 

California, which is the country’s largest cannabis market, already requires cannabis products to have a warning that use while pregnant or breastfeeding may be harmful. This new vote means the labeling, both on the packages and in the stores that sell them, will become even more specific, according to Woodruff. 

“The warning labels have to be put in places where these products are sold, and they have to say that it’s known to the state of California to cause developmental health effects,” Woodruff said. “And I know the system has been changing over time, so they may put more specificity on that. It’s unclear.” 

Legal access to cannabis in the U.S. means more women are grappling with whether to consume the plant while pregnant. The percentage of pregnant women in the U.S. self-reporting cannabis use climbed from 3.4% in 2002-2003 to 7% in 2016-2017, according to a study published in June in the Journal of the American Medical Association. Similar information was found in a study released in July examining self-reported use among women in Northern California, finding an increase of cannabis use during pregnancy from 1.95% in 2009 to 3.38% in 2017.

Many cannabis advocates are concerned about the effects this committee’s decision will have on California’s growing cannabis industry. Some also question the legitimacy of the studies the committee looked at to come to this decision. 

Ellen Komp, the deputy director of California NORML, a legal pot advocacy group, told the panel she thought the studies were limited, looking only at women who smoked cannabis and not those whoo ingested the plant in other ways, such as via vapes, topical lotions, or edibles. She said all of the studies together presented “conflicting results,” according to a KTLA 5 story.

The California Cannabis Industry Association spokesman said this could create an opportunity for lawyers and consumers to take advantage of those in the cannabis industry and that, since cannabis is still considered a Schedule I substance, research on the plant’s effect are limited. 

“Good policy and consumer protections are based on facts and data,” California Cannabis Industry Association’s spokesman Josh Drayton said.

Although the exact labeling and regulations around labeling is still being decided, businesses have a one-year grace period to add the warnings before they will be required state-wide.

Photo by Dimitri Bong via Unsplash