Cannabis use and measurement of cannabinoids in plasma and breast milk of breastfeeding mothers

Background Information on cannabinoids in breast milk and maternal cannabis use is limited. We quantified cannabinoids in plasma and breast milk of breastfeeding mothers and assessed cannabis use patterns. Methods This is a prospective study at a university hospital in a state with legal medical and recreational cannabis. Breast milk and plasma samples along with survey data were collected from volunteers using cannabis in the last 48 h at 2 weeks and 2 months postpartum. Results Twenty subjects were enrolled. Median age (IQR) was 27 (24–34) years. Median (IQR) instances of cannabis use in the last 7 days were visit 1: 17 (6–29) and visit 2: 23 (15–45). Median (IQR) tetrahydrocannabinol (THC) concentrations were: plasma 3.7 ng/ml (0.8–56.8) and breast milk 27.5 ng/ml (0.8–190.5). Median (IQR) cannabidiol (CBD) concentrations were: plasma 0.6 ng/ml (0.5–6.4) and breast milk 1.2 ng/ml (0.5–17.0). Median (IQR) THC M/P: 7.0 (1.8–34.6) and CBD M/P: 2.6. Median breast milk THC concentration increased from visit 1 to visit 2 by 30.2 ng/ml (95% CI 3.05–69.3 ng/ml). Conclusions THC and CBD accumulate in breast milk. Breastfeeding mothers used cannabis frequently and increased use in the early postpartum period. Research on the effects of infant exposure to cannabinoids in breast milk is urgently needed. Impact Cannabis use is increasing in the general population and many nursing mothers use cannabis. THC has been previously detected in breast milk but little is known on how it concentrates relative to plasma. Data on cannabinoids other than THC, reasons for cannabis use, and patterns of use in breastfeeding women are also limited. We detected THC and CBD in breast milk. Both concentrate in breast milk relative to plasma. We showed that breastfeeding mothers increased cannabis use in the weeks after childbirth. Further research is needed to evaluate infant exposure to cannabinoids via breast milk and effects on infant health.