evidence: The medicinal and psychoactive properties of marijuana are mediated by compounds called cannabinoids, which are absorbed from the lungs when smoked or from the gastrointestinal tract when ingested. Tetrahydrocannabinol (THC) is a small and highly lipophilic molecule that is distributed rapidly to the brain and fat. Metabolized by the liver, the half-life of THC varies from 20–36 hours in occasional users to 4–5 days in heavy users and may require up to 30 days for complete excretion. In animal models, THC crossed the placenta, producing fetal plasma levels that were approximately 10% of maternal levels after acute exposure. Significantly higher fetal concentrations were observed after repetitive exposures 9. Limited human data suggest that THC also appears in breast milk 10. [...] These findings were more pronounced among women who used more marijuana, particularly during the first and second trimesters 34 36 39. The clinical significance of these observations remains uncertain. [...] Effects of Marijuana Use on Lactation