Fetal exposure

Fetal exposure is the transfer of a substance from a pregnant person's bloodstream across the placenta to the developing fetus.

Cannabinoids cross the placenta readily because they are small and fat-soluble, and the fetal brain expresses cannabinoid receptors from early gestation, when the endocannabinoid system helps guide how neurons grow and connect. Prenatal cannabis exposure has been associated in observational studies with lower birth weight, preterm birth and later differences in attention and behavior, though separating cannabis from tobacco, alcohol and other factors is difficult. Almost all of that research concerns THC-containing cannabis; there is very little human data on cannabidiol alone.

Obstetricians screen for substance use at prenatal visits, and U.S. health agencies advise against any cannabis or cannabinoid use during pregnancy because no safe level has been established. Cannabidiol carries its own animal-study signals, including effects on male reproductive development, and the U.S. Food and Drug Administration specifically cautions against its use in pregnancy. Pregnancy is therefore one of the few areas where regulators have issued a specific caution about cannabidiol rather than a general call for more research.