The effect on babies whose mothers consume cannabis while they are in the womb or breastfeeding is inconsistent and not fully understood: research from the 1980s that suggested children born to cannabis-using mothers might experience long-term cognitive deficits, haven’t been replicated in more recent studies for example, though a 2014 study suggested that THC might interfere with developing neural connections in the developing brain .
Either way the need for caution has been underlined by new evidence from researchers at the University of Colorado and the University of Utah that found THC (the psychoactive component of cannabis) stays in breast milk much longer than previously recognized — a full six weeks, which contrasts with the six days reported previously by the American Academy of Pediatrics (AAP).
In the present study, researchers studied 25 women who gave birth at two Colorado hospitals between November 2016 and June 2019, all of whom had used weed at some point during their pregnancy and intended to breastfeed their children.
Each subject was asked to abstain from cannabis for six weeks after giving birth, and seven women quit weed completely while the study was ongoing. Researchers collected blood, urine, and breast milk samples from each subject over the course of the study.
The results from the study found THC was present in every mother’s breast milk for as long as six weeks after they last used cannabis. The exact concentration of THC in each sample of breast milk was different, likely due to each woman's unique metabolism, weight, and the amount of pot they used.
Despite the findings of the study being limited by the small study size, the results are nonetheless concerning.
“This study provided invaluable insight into the length of time it takes a woman to metabolize the THC in her body after birth, but it also helped us understand why mothers use marijuana in the first place,” explained Maya Bunik, MD, MPH, medical director of the Child Health Clinic and the Breastfeeding Management Clinic at Children’s Colorado.
These reasons include nausea, pain and sleep issues; a previous investigation found that 70 percent of Colorado dispensaries recommended weed to expecting mothers.