News & Politics

Here's How Long Traces of Marijuana Can Remain in Breast Milk

With marijuana legalization becoming more widespread, these questions are growing in importance.

Photo Credit: Chuck Grimmett

Marijuana is rapidly becoming legal across the United States as citizens and lawmakers question the wisdom of outlawing a drug that is, by almost any conceivable measure, much less dangerous than alcohol.

But "less dangerous" doesn't mean "risk-free," and the increasing ubiquity of legal pot raises serious medical and health questions that we are only beginning to unravel.

For example, there's little data about the impact of infants' exposure to marijuana through breast milk. Because of this lack of clarity, doctors recommend completely abstaining from marijuana use while breastfeeding.

A new study from researchers at the University of California San Diego School of Medicine suggests there's a good basis for this recommendation. In a study of 50 women who were users of marijuana, researchers were able to detect THC in breast milk for as long as six days after the mother's last usage. THC is the chemical that can produce psychoactive effects in marijuana users.

"We found that the amount of THC that the infant could potentially ingest from breast milk was relatively low, but 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 Christina Chambers, the principal investigator on the study. "The ingredients in marijuana products that are available today are thought to be much more potent than products available 20 or 30 years ago."

For those skeptical of any drug use, it might seem pointless to study the trace amounts of marijuana in breast milk when parents could just avoid using the drug at all. But Chambers argued that telling parents they must choose between breastfeeding and marijuana use can be difficult for doctors.

"Pediatricians are often put into a challenging situation when a breastfeeding mother asks about the safety of marijuana use," she said. "We don't have strong, published data to support advising against use of marijuana while breastfeeding, and 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."

There are still many more questions Chambers would like to explore with this research.

"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 asks. "These are critical areas where we need answers as we continue to promote breast milk as the premium in nutrition for infants."

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Cody Fenwick is a reporter and editor. Follow him on Twitter @codytfenwick.