Marijuana stays in breast milk for up to six weeks, small study shows

• THC can stick around in breast milk up to six weeks after quitting, a small study suggests.
• It didn't look at how that affected babies, but other work has linked THC with negative effects.
• The findings show women need support stopping cannabis use during pregnancy and breastfeeding.

People who use marijuana during pregnancy but stop after birth may still transmit THC to their babies through breast milk for up to six weeks, a small study in JAMA Pediatrics showed.

The study didn't look at if or how the babies were affected, but the study authors from Children's Hospital Colorado said they were "concerned" about the drug's potential impact.

The findings align with recommendations from the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists to abstain from cannabis use while pregnant or breastfeeding.

Only seven women were able to abstain from cannabis for six weeks

To conduct the study, researchers recruited women who'd used marijuana during pregnancy, planned to breastfeed, and agreed to abstain from the substance for six weeks after birth while supplying milk, blood, and urine samples.

Most smoked weed about twice a week during pregnancy.

While 25 women initially enrolled, only seven completed the study without using marijuana. The rest, who tended to be younger and less educated, said they couldn't abstain due to stress, sleep, and pain.

The researchers found all seven abstainers had detectable THC in their milk and plasma even by the end of the six weeks. The concentration of THC generally increased the first two weeks before slowly decreasing over the rest, perhaps reflecting the changing makeup of breast milk.

The study showed new moms who use marijuana need more support

The study was small and didn't assess exactly how much marijuana the moms were consuming during pregnancy. Since most women smoked, there's also more to learn about how other methods of cannabis consumption may affect breast milk.

But the findings revealed just how long THC can stick around in breast milk and plasma after regular use, while past studies have mostly only looked at how long it lasts after single use. Only one known report has also looked at THC in breast milk relative to plasma.

The current findings also suggest that advice to discard breast milk that may have traces of THC in it is unrealistic and that pregnant people and new moms who want to quit need more support.

"To move forward, we need to be less judgmental and more realistic about how we're going to help women have alternative tools to deal with the symptoms they were using the substances for in the first place," Tessa Crume, a researcher at the University of Colorado's School of Public Health who was not involved in the study, previously told Insider.

Cannabis use in pregnancy has been linked to behavioral problems in kids

Current recommendations to avoid marijuana during pregnancy and breastfeeding are based on past research linking THC with negative outcomes in babies.

In an April study - the largest of its kind to date - researchers found that pregnant women with cannabis use disorder were more likely to deliver premature, underweight, and small-for-gestational-age babies than moms without the condition. Their babies even had a higher risk of death within the first year of life, though fortunately that was rare.

Past studies have found an association between cannabis use in pregnancy and children with lower IQs, attention problems, and more impulsiveness. Experts say these connections are due it part to how the compound can disrupt the endocannabinoid system, which plays a key role in supporting a healthy pregnancy and fetal brain development.

Still, research on cannabis use in pregnancy has limitations, namely that it's tough to control for other factors that may affect the outcomes like socioeconomic status, diet, and stress.