Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk

Marijuana is the most commonly used recreational drug among breastfeeding women. With legalization of marijuana in several US states and a 1990 study in which authors documented psychomotor deficits in infants breastfed by mothers using marijuana, there is a need for information on potential exposure to the breastfed infant. Our objective with this study was to quantify cannabinoids in human milk after maternal marijuana use.METHODS:Between 2014 and 2017, 50 breastfeeding women who reported marijuana use provided 54 breast milk samples to a research repository, Mommy's Milk. Concentrations of -9-tetrahydrocannabinol (9-THC), 11-hydroxy--9-tetrahydrocannabinol, cannabidiol, and cannabinol were measured by using liquid chromatography mass spectrometry electrospray ionization.RESULTS:9-THC was detectable in 34 (63%) of the 54 samples up to approximate to 6 days after last reported use; the median concentration of 9-THC was 9.47 ng/mL (range: 1.01-323.00). Five samples had detectable levels of 11-hydroxy--9-tetrahydrocannabinol (range: 1.33-12.80 ng/mL) or cannabidiol (range: 1.32-8.56 ng/mL). The sample with the highest concentration of cannabidiol (8.56 ng/mL) did not have measurable 9-THC. Cannabinol was not detected in any samples. The number of hours since last use was a significant predictor of log 9-THC concentrations (-0.03; 95% confidence interval [CI] -0.04 to -0.01; P = .005). Adjusted for time since last use, the number of daily uses and time from sample collection to analysis were also significant predictors of log 9-THC concentrations (0.51; 95% CI 0.03 to 0.99; P = .039; 0.08; 95% CI 0.00 to 0.15; P = .038, respectively).CONCLUSIONS:9-THC was measurable in a majority of breast milk samples up to approximate to 6 days after maternal marijuana use.