In fact, they estimated that babies receive 2.5 percent of their mother’s dose, which are just micrograms of the drug. However, they said the amount is still concerning.
“The long-term neurobehavioral effect of exposure to delta-9-tetrahydrocannabinol on the developing brain is unclear,” the authors wrote. “Mothers should be cautious using cannabis during pregnancy and breastfeeding.”
The Centers for Disease Control and Prevention advises against using marijuana when pregnant, planing to become pregnant and breastfeeding, as THC can negatively affect a baby's development.
While the data on the effects of marijuana exposure through breastfeeding is limited, previous research shows it can cause low birth weight and even learning difficulties as the child becomes older.