With the legalization of marijuana in several US states, increased use has been seen in pregnant and breastfeeding women for both medicinal and recreational purposes. Although national organizations like the American Academy of Pediatrics recommend breastfeeding mothers do not use marijuana, there has been a lack of current data to support any health or neurodevelopmental concerns in infants as a result of exposure to tetrahydrocannabinol (THC) or other components of marijuana via breast milk.

“Pediatricians are often put into a challenging situation when a breastfeeding mother asks about the safety of marijuana use. We don’t have strong, published data to support advising against use of marijuana while breastfeeding, and if women feel they have to choose then we run the risk of them deciding to stop breastfeeding – something that we know is hugely beneficial for both mom and baby,” said Christina Chambers, PhD, MPH, principal investigator of the study, program director of Mommy’s Milk, and co-director of the Center for Better Beginnings.

Cannabinoids, marijuana’s active compounds, such as THC, like to stick to fat, which is abundant in breast milk. This stickiness has suggested that in women who use marijuana, these compounds can end up in breast milk, raising concerns about their potential effects on nursing babies.

To better understand how much marijuana actually gets into breast milk and how long it stays there, our Mommy’s Milk team conducted a study published online today in the journal Pediatrics. We examined 54 breast milk samples from 50 women who used marijuana either daily, weekly or sporadically – with inhalation being the primary method of intake. THC, the primary psychoactive component of marijuana, was detected in 63 percent of the breast milk samples up to six days after the mother’s last reported use.

“We found that the amount of THC that the infant could potentially ingest from breast milk was relatively low, but in some mothers could be detected as long as six days after the mother last used marijuana. We still don’t know enough about the drug to say whether or not there is a concern for the infant at any dose, or if there is a safe dosing level,” said Dr. Chambers. “The ingredients in marijuana products that are available today are thought to be much more potent than products available 20 or 30 years ago.”

Dr. Chambers believes that the results are a stepping stone for future research. More studies need to be done not only to determine the long-term impact for children, if any, of marijuana in breast milk, but more specifically, “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? These are critical areas we need answers to as we continue to promote breast milk as the premium in nutrition for infants.”

Study co-authors include: Kerri Bertrand, MPH; Nathan Hanan, PharmD; Gordon Honerkamp-Smith, MS; and Brookie Best, PharmD, MAS, all with UC San Diego.

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