evidence: Some AZ health care providers and parents have asked questions about whether medical marijuana is safe for use while breastfeeding. The short answer is no, because the active chemical in marijuana is passed to the baby through breast milk. For this reason, most experts, including the American Academy of Pediatrics and the CDC advise moms not to use marijuana (medical or not) while breastfeeding. Tetrahydrocannabinol (the psychoactive ingredient in Cannabis) stays in the body for four to six weeks. It’s found in the urine of breastfeeding babies whose mothers use marijuana. It’s also fat soluble, which means it builds up with chronic use and can be stored in fat tissue for months. We also know that babies are much more vulnerable than adults to illness, infection, chemicals, and so on. That alone is a good reason to avoid marijuana and anything else potentially harmful that can enter your baby’s body through your milk.