Researchers at Children’s Hospital Colorado say their study showing THC stays in breast milk for up to six weeks supports earlier recommendations by some medical bodies to not use cannabis while pregnant or breastfeeding.
The concentrations of THC varied from woman to woman, likely depending on their level of use, body mass index and metabolism, notes a statement from Children’s Colorado. Even so, “THC was excreted in the breast milk of these seven women for up to six weeks. In fact, all of the women still had detectable levels of THC in their breast milk at the end of the study,” researchers report.
Published Monday in JAMA Pediatrics, investigators sought to estimate the amount and duration of THC excretion in breast milk among women with known prenatal cannabis use, representing the first such examination since a 1982 study in the New England Journal of Medicine.
Investigators screened adult women with prenatal cannabis use — had a history of use during pregnancy and/or a positive urine test for THC when admitted for delivery — at Children’s Colorado and UCHealth’s University of Colorado Hospital between Nov. 1, 2016 and June 30, 2019.
Twenty-five women were enrolled after voicing their intention to breastfeed, their willingness to abstain from marijuana use for six weeks after delivery and their ability to provide milk, blood and urine samples during those six weeks. But just seven women were able to abstain from using cannabis for the duration of the study, with those unable to do so citing the need for stress, sleep and pain relief.
THC crosses the placenta, is highly lipophilic and can be detected in breast milk, having sparked national guidelines that recommend “abstinence from marijuana use during pregnancy and lactation,” notes the study abstract. Recommendations to abstain from cannabis use have been put forward by the American Academy of Pediatrics, the American College of Obstetricians and Gynecologists and the Academy of Breastfeeding Medicine.
Doctors are seeing more maternal cannabis use during pregnancy in line with the greater use of weed in society as a whole, Children’s Colorado reports.
“However, given the lack of scientific data regarding how long THC persists in breast milk, it was challenging to provide mothers with a definitive answer regarding the safety of using marijuana while breastfeeding and simply ‘pumping and dumping’ until THC was no longer detectable in their milk,” Dr. Erica Wymore, the study’s primary investigator and a neonatologist at Children’s Colorado, says in the statement.
Beyond getting more information on how long THC remains in breast milk, the study also sheds light on “why mothers use marijuana in the first place,” says Dr. Maya Bunik, a senior investigator for the study and medical director of the Child Health Clinic and the Breastfeeding Management Clinic at Children’s Colorado.
“To help encourage successful abstention, we need to look at — and improve — the system of supports we offer new moms,” Dr. Bunik emphasizes.
And “to limit the unknown THC effects on foetal brain development and promote safe breastfeeding, it is critical to emphasize marijuana abstention both early in pregnancy and postpartum,” she adds.
Although the study wasn’t meant to explore the impact of marijuana use on infants, the results are concerning, particularly given that “today’s marijuana is five to six times higher in potency than what was available prior to recent marijuana legalization in many states,” notes Dr. Wymore.
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