Study reveals weed stays in breast milk for longer than you think

That’s too long to “pump and dump”

How long does weed stay in breastmilk

Online support groups are filled with women who recommend marijuana for new mothers struggling with nausea or stress. But how long does THC stay in your system? The answer may have you thinking twice about whether it’s ok to mix weed with breastfeeding.

A study published on August 27 in Pediatrics reveals that low levels of weed can be found in breastmilk up to six days after the mother smoked — or even after eating an edible. This is the first major study to provide an answer to the crucial question of how long it takes for weed to leave your system when it comes to breastmilk.

Even edibles could leave trace amounts of THC in your breastmilk.


But don’t throw out your special brownies just yet, because it’s still unclear whether the chemicals found in breastmilk actually have a negative effect on child development. At least, that’s what senior study author Christina Chambers tells Inverse.

“It’s really important to be able to gather more information on marijuana so that pediatricians can know what to say, with good evidence to back that up, and moms can make better decisions,” says Chambers, a pediatric researcher at the University of California, San Diego who also helps run a counseling service called MotherToBaby.

How much THC is in breastmilk?

To better understand how much marijuana or its active chemicals actually get into breast milk and how long they remain, Chambers and her team analyzed samples donated by 54 women to a breast milk repository between 2014 and 2017. The women also answered questions about their use of marijuana, prescription medications, and other substances in the 14 days before their milk samples were collected.

The researchers found that tetrahydrocannabinol or THC, the main mind-altering substance in marijuana, was detectable in 34 samples, or 63 percent of the breast milk samples for up to six days after the mother’s last reported use. The average concentration: 9.47 nanograms of THC per milliliter of breast milk.

That may seem like a really small amount, especially considering that a baby will only actually ingest about one percent of that THC, but previous research in rodents indicates that even small amounts of THC can impair concentration, attention, memory, and problem-solving abilities, according to Dr. Teresa Baker, an associate professor in the Department of Obstetrics and Gynecology at Texas Tech University Health Sciences.

“If a drug is producing physiological symptoms in the mom, it’s probably in large enough quantities that we should be concerned about her breast milk too,” Baker says.

Nevertheless, rodents are not humans, and there haven’t been enough long-term studies in humans to determine the cognitive, intellectual, and behavioral effects of THC in children, she says.

How long does weed stay in your breastmilk?

How long does THC stay in breastmilk?


Given the uncertainty of the drug’s effects, the duration it takes to get it completely out of one’s system may be even more important. For example, mothers may be able to drink a cup of coffee and their bodies will metabolize get rid of all the caffeine in a few hours. During that time mothers may decide to skip a feeding, or they may decide to “pump and dump” the breast milk, Chambers says. But because of the way marijuana metabolizes and dissolves easily in fat, THC and other compounds stay in the body longer. Studies show that in daily users, compounds from cannabis are detectable in bodily fluids for up to 30 days after last use. Moms who regularly smoke or ingest pot may not have the option to “pump and dump.”

Moreover, because the study did not specifically track when mothers consumed cannabis, it may be possible that the levels of THC that babies are exposed to in breast milk are much higher immediately after use.

But because breast milk can be extremely beneficial to infants, researchers agree that moms who smoke weed should not give up breastfeeding either. “It puts pediatricians in a really awkward position,” Chambers says. That’s why it’s so important to find out how marijuana can affect a breastfeeding mother’s milk supply — and for how long, she says.

However, until we know more, the American Academy of Pediatrics recommends that mothers simply avoid marijuana during pregnancy and while breastfeeding.

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