Research shows marijuana THC stays in breast milk for six weeks

Tetrahydrocannabinol (THC), the psychoactive component of marijuana, can linger in breast milk for up to six weeks, says a new study published in the journal JAMA paediatrics.

Women with prenatal marijuana use who delivered their infants at Children's Colorado and UC Health's University of Colorado Hospital between November 1, 2016, and June 30, 2019, were observed closely.

Researchers at Children's Hospital Colorado conducted the study on 25 women who were over the age of 18, had a history of marijuana use during pregnancy, had an intention to breastfeed, were willing to abstain from marijuana use for six weeks after delivery and were willing to provide milk, blood and urine samples during those six weeks.

Out of the 25 enrolled, seven women were able to abstain from marijuana use during the study period.

The research found that though the level of THC varied from woman to woman depending on their level of use, BMI and metabolism, the women still had detectable levels of THC in their breastmilk for up to six weeks.

After a study held in 1982 in the New England Journal of Medicine, this is the first study to examine the THC in breastmilk and plasma among women with known marijuana use in pregnancy.

The researchers, after the study, strictly advised women to stay away from marijuana during their pregnancy and breastfeeding years. They also expressed their concerns about the impact the drug could have on the baby.

"This study was not about the impact marijuana has on babies, but we are concerned. Especially when we consider that today's marijuana is five to six times higher in potency than what was available prior to recent marijuana legalization in many states," said Erica Wymore, primary investigator and neonatologist at Children's Colorado.