Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk

Abstract

BACKGROUND AND OBJECTIVE: 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 Δ-9-tetrahydrocannabinol (∆9-THC), 11-hydroxy-Δ-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 ∼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-Δ-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 ∼6 days after maternal marijuana use.