For new moms experiencing nausea — or simply those who are stressed out — online support groups are filled with women citing the benefits of marijuana. But despite the growing acceptance of cannabis, research suggests that women who are pregnant or breastfeeding should avoid the drug.

A study published Monday in the journal Pediatrics found that low levels of the chemicals in marijuana were measurable in breast milk up to six days after women had smoked pot or eaten an edible. There’s long been a lack of research into the area but this new study signals that it Marijuana may stay in breast milk longer than some mothers may think.

However, it’s not clear whether these chemicals negatively affect child development yet, 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.

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.

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 body 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 mom’s 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.