Recreational Cannabis Use During Human Pregnancy: Its Effects on the Placenta and Endocannabinoid System

The use of cannabis during pregnancy is increasing, in line with its growing societal acceptance and legalization. Cannabis use mainly concerns its active components Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). While cannabis has therapeutic effects on pain, nausea, and vomiting, its impact on fetal development remains a significant public health concern. Given the existence of a local endocannabinoid system (ECS) in the placenta, with proven effects on placental development and blood flow, it is likely that THC and CBD exert effects via interference with the placental ECS. This review summarizes how cannabis use affects the placental ECS and describes the consequences of such use on placental function and fetal development. It starts with discussing the placental ECS, the effects of THC and CBD on placental function, and the pharmacokinetics of cannabinoids during pregnancy. It then describes the effects of both paternal and maternal cannabis use and provides epidemiological data linking placental insufficiency, impaired fetal growth, and preeclampsia to cannabis use. It also raises awareness for the possibility that cannabis use, by altering DNA methylation, might result in transgenerational effects. It is concluded that current evidence supports abstaining from cannabis use during preconception, pregnancy, and lactation to optimize maternal, fetal, and intergenerational health outcomes.