Breastfeeding moms who smoke marijuana expose their infants to cannabinoids

Michael G Burke, MD

Women who use marijuana while breastfeeding produce breast milk with a measurable amount of the primary psychoactive ingredient in marijuana, delta-9-tetrahydrocannabinol (delta 9-THC), for up to 6 days since they last smoked. This was the primary finding in a study in 50 breastfeeding women who reported using marijuana and provided breast milk samples to a research repository for analysis.

Two-thirds of participants were breastfeeding a child aged younger than 1 year, and 88% reported using marijuana at least once a day, most often exclusively through smoking (64%). Delta 9-THC was detectable in about two-thirds of milk samples with a median concentration of 9.47 ng/mL. Far fewer samples, only 9%, had measurable concentrations of either of 2 other cannabinoids in marijuana-11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC) or cannabidiol-and only 1 sample had measurable levels of all 3 cannabinoids.

Both the number of hours since last marijuana use and number of uses per day were predictors of Delta 9-THC concentrations in breast milk. Concentrations declined by 3% each hour after exposure, and as the number of uses per day increased so did the concentrations (Bertrand KA, et al. Pediatrics. 2018;142[3]:e20181076).

Thoughts from Dr. Burke

To date, 9 states have legalized recreational use of marijuana and 30 allow dispensing marijuana for medical purposes. These researchers show that some psychoactive components of marijuana are transferred to breastfed babies, but we still don’t know what this means for the baby’s health and neurologic development. The American Academy of Pediatrics (AAP) recommends a conservative approach to screening for marijuana use and advising against it for pregnant and breastfeeding women. For all the AAP’s recent recommendations on the topic, see: Pediatrics. 2018;142(3):e20181889.