Study: THC remains in breast milk for up to 6 weeks

In a new study published in the journal JAMA Pediatrics, researchers at Children's Hospital Colorado have discovered that the THC remains in breast milk for up to 6 weeks, supporting the recommendations to avoid using cannabis during pregnancy and while breastfeeding.

THC concentrations varied from woman to woman, likely depending on their level of consumption, body mass index, and metabolism. Even so, «THC was excreted into 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,» the researchers report.

This research is the first of its kind since a previous study conducted in 1982 in the New England Journal of Medicine.

A strict protocol

The researchers identified adult women with a history of prenatal cannabis use—that is, women who had used cannabis during pregnancy and/or tested positive for THC in a urine test upon admission for delivery— between November 1, 2016, and June 30, 2019. .

Twenty-five women were enrolled after expressing their intention to breastfeed, their willingness to abstain from using cannabis for 6 weeks after giving birth, and their ability to provide milk, blood, and urine samples during those 6 weeks. However, only 7 women were able to abstain from using cannabis for the duration of the study; those who were unable to do so cited the need to manage stress, improve sleep, and relieve pain.

THC crosses the placenta, is highly lipophilic, and can be detected in breast milk; hence the recommendations to abstain from cannabis use «during pregnancy” »and breastfeeding," notes the study's abstract.

«However, given the lack of scientific data on how long THC persists in breast milk, it was difficult to give mothers a definitive answer regarding the safety of cannabis use while breastfeeding and simply to «pump and dump» until THC was no longer detectable in their milk,» explains Dr. Erica Wymore, the study’s principal investigator and a neonatologist at Children’s Colorado.

Insight into the Reasons for Cannabis Use During Pregnancy

In addition to providing more information on how long THC remains in breast milk, the study also sheds light on «why mothers use cannabis in the first place.».

«To help promote successful abstinence, we need to examine—and improve—the support we offer new mothers,», emphasizes Dr. Maya Bunik, the study’s principal investigator and medical director of the Child Health Clinic. and the breastfeeding clinic at the Children's Colorado Hospital.

«To limit the unknown effects of THC on fetal brain development and promote safe breastfeeding, it is essential to emphasize abstinence from cannabis during early pregnancy and the postpartum period,» she adds.