The American Academy of Pediatrics (AAP) has issued a warning to breastfeeding women against using cannabis. Citing a recent AAP study published in the journal Pediatrics, new research suggests that THC can be transferred through breast milk up to six days after consumption. 

According to the New York Times, researchers at the University of California San Diego compiled breast milk samples from 50 postnatal women who self-reported cannabis use. Of the 54 tested samples, study authors said that 34 (63%) tested positive for THC.

Cannabis use during and after pregnancy has been a contentious topic throughout America’s recent experiment with marijuana legalization. Despite early research indicating that marijuana’s psychoactive properties can be carried onto an unborn child and potentially affect development, those studies have been hindered by the drug’s federally prohibited status and have only resulted in preliminary data. 

On the other end of the spectrum, women across the world have reported finding relief from the pain, stress, and sleeplessness of pregnancy through pot. Because long-term studies into potential development issues caused by infant cannabis exposure have not been conducted, the discourse around cannabis and pregnancy is not demonized in the same way that natal alcohol use currently is — at least not yet.

But even without firm data detailing potential birth defects or developmental disorders, the new study on marijuana and breastfeeding was clear enough for the AAP to take an official stance, warning breastfeeding women to avoid the controversial plant.

“The fact that marijuana is legal in many states may give the impression the drug is harmless during pregnancy, especially with stories swirling on social media about using it for nausea with morning sickness,” Sheryl A. Ryan, chairwoman of AAP’s Committee on Substance Use and Prevention, told the Times. “But in fact, this is still a big question.”

But as breastfeeding advocates around the world continue to fight baby formula lobbyists, insisting on the medical and developmental benefits of the practice, experts worry that mothers could respond to the new data by ceasing breastfeeding instead of stopping marijuana use. 

“This creates a dilemma for pediatricians who want their patients to be breast-fed and worry that some mothers, if told not to use cannabis, may not breastfeed,” Christina D. Chambers, a professor of pediatrics at the University of California San Diego, and one of the authors of the study, told the Times.

Like the rest of the scientific community, AAP researchers are still waiting for nationwide cannabis descheduling before comprehensive, widespread studies can be legally conducted.