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

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.