How Long After Smoking Weed Can You Breastfeed Again?

Marijuana compounds can stay active in breastmilk up to a week after mothers smoked it, scientists warn.

Originally Published: 
Close up of a woman smoking weed.
Mayara Klingner / EyeEm / Getty

Breastfeeding people who smoke marijuana can pass THC, the primary psychoactive component in marijuana, to their babies nearly a week after use, new research suggests. Although the American Academy of Pediatrics already recommends mothers refrain from smoking weed while breastfeeding, the findings are the first to demonstrate that using cannabis and then waiting a few hours, or even days, to breastfeed may not cut it.

“Pediatricians are often put into a challenging situation when a breastfeeding mother asks about the safety of marijuana use,” study author Christina Chambers, Ph.D., a pediatrics professor at the UC San Diego School of Medicine and director of clinical research at Rady Children’s Hospital-San Diego, said in a statement. “If women feel they have to choose, we run the risk of them deciding to stop breastfeeding — something we know is hugely beneficial for both mom and baby.”

Early breastfeeding has been linked with reduced risk of asthma, obesity, and sudden infant death syndrome, along with improved health and intelligence later in life, research shows — and that’s just for the babies. There’s evidence that breastfeeding is good for moms as well, and it may lower their risk for developing breast and uterine cancers, as well as type 2 diabetes. The message is clear: If moms can breastfeed, they should.

Unless, of course, breastfeeding passes dangerous chemicals to their babies. The question of marijuana use has long plagued the medical community. Can a mom smoke up between pumps? And how long after a hit can she feed her baby again?

To get a better idea of what could actually happen when breastfeeding moms get high, Chambers and colleagues collected 54 breastmilk samples from 50 women who smoked marijuana either daily, weekly, or sporadically. THC was found in 63% of the breastmilk samples for up to six days after self-reported use. Although researchers note that the amount of THC was relatively low, they can’t say whether even trace amounts of it are safe for newborns.

The findings raise important questions for parents about pot use — especially those who see it as a healthier alternative to alcohol. However, more research is needed to uncover any long-term risks of mixing THC with breastmilk, Chambers says.

“Are there any differences in effects of marijuana in breast milk for a two-month-old versus a 12-month-old, and is it different if the mother smokes versus eats the cannabis?” she says. “These are critical areas where we need answers as we continue to promote breastmilk as the premium in nutrition for infants.”

This article was originally published on