THC and CBD concentrated in breast milk at levels much higher than in blood
In 20 breastfeeding mothers who used cannabis, THC accumulated in breast milk at a median concentration 7 times higher than in plasma, and mothers increased their cannabis use in the early postpartum period.
Quick Facts
What This Study Found
Median breast milk THC concentration was 27.5 ng/ml vs 3.7 ng/ml in plasma, a milk-to-plasma ratio of 7.0. CBD also concentrated in breast milk (M/P ratio 2.6). THC in breast milk increased by 30.2 ng/ml from visit 1 (2 weeks) to visit 2 (2 months). Mothers used cannabis frequently, with a median of 17-23 instances per week.
Key Numbers
20 subjects; median THC: plasma 3.7 ng/ml, milk 27.5 ng/ml; THC M/P ratio 7.0; CBD M/P ratio 2.6; cannabis use 17-23 instances/week; breast milk THC increased by 30.2 ng/ml from 2 weeks to 2 months
How They Did This
Prospective study at a university hospital in a state with legal cannabis. Twenty breastfeeding mothers who used cannabis in the last 48 hours provided breast milk and plasma samples at 2 weeks and 2 months postpartum, along with survey data on use patterns.
Why This Research Matters
With increasing cannabis legalization and use during breastfeeding, quantifying how cannabinoids concentrate in breast milk is essential. The 7-fold concentration of THC relative to plasma means infants may receive meaningful cannabinoid exposure.
The Bigger Picture
The finding that cannabis use increased in the early postpartum period, combined with high milk-to-plasma ratios, means infant exposure may actually increase over the first two months of life, a period of critical neurodevelopment.
What This Study Doesn't Tell Us
Small sample of 20 self-selected cannabis users. No measurement of infant cannabinoid levels. No assessment of infant health outcomes. Cannot determine clinical significance of exposure levels.
Questions This Raises
- ?What are the actual infant blood levels resulting from breastfeeding exposure?
- ?Does cannabinoid exposure via breast milk affect infant neurodevelopment?
- ?How long do cannabinoids persist in breast milk after the last use?
Trust & Context
- Key Stat:
- THC in breast milk was 7x higher than in blood plasma
- Evidence Grade:
- Prospective design with paired plasma and milk measurements, though small sample and no infant outcome data.
- Study Age:
- Published in 2021.
- Original Title:
- Cannabis use and measurement of cannabinoids in plasma and breast milk of breastfeeding mothers.
- Published In:
- Pediatric research, 90(4), 861-868 (2021)
- Authors:
- Moss, Michael J, Bushlin, Ittai, Kazmierczak, Steven, Koop, Dennis, Hendrickson, Robert G, Zuckerman, Katharine E, Grigsby, Tamara M
- Database ID:
- RTHC-03366
Evidence Hierarchy
Enrolls participants and follows them forward in time.
What do these levels mean? →Frequently Asked Questions
Does THC get into breast milk?
Yes. This study found THC concentrated in breast milk at a median 7 times higher than in the mother's blood plasma, and CBD also accumulated in milk at about 2.6 times plasma levels.
Did mothers use more cannabis after giving birth?
Yes. Mothers increased their cannabis use in the early postpartum period, and breast milk THC concentrations were significantly higher at 2 months compared to 2 weeks postpartum.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-03366APA
Moss, Michael J; Bushlin, Ittai; Kazmierczak, Steven; Koop, Dennis; Hendrickson, Robert G; Zuckerman, Katharine E; Grigsby, Tamara M. (2021). Cannabis use and measurement of cannabinoids in plasma and breast milk of breastfeeding mothers.. Pediatric research, 90(4), 861-868. https://doi.org/10.1038/s41390-020-01332-2
MLA
Moss, Michael J, et al. "Cannabis use and measurement of cannabinoids in plasma and breast milk of breastfeeding mothers.." Pediatric research, 2021. https://doi.org/10.1038/s41390-020-01332-2
RethinkTHC
RethinkTHC Research Database. "Cannabis use and measurement of cannabinoids in plasma and b..." RTHC-03366. Retrieved from https://rethinkthc.com/research/moss-2021-cannabis-use-and-measurement
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.