Responding to the legalization of marijuana in a growing number of states in America, the American Academy of Pediatricians (AAP) released their first-ever guidelines on pot use during pregnancy or while breastfeeding. "Women should definitely be counseled that it's not a good idea to use marijuana while pregnant," Dr. Seth Ammerman, a clinical professor of pediatrics at Stanford who worked on the report, tells The Los Angeles Times. "If you're breastfeeding, we would encourage you to cut back or quit." Due to marijuana's current classification as a Schedule 1 drug, the researchers acknowledge there are a lack of studies on the effects of pot use during pregnancy or lactation. However, in the guidelines published last week in the journal Pediatrics, authors from the AAP say available findings on THC indicate it's risky for babies' developing brains. "The importance of the published findings and the emerging research regarding the potential negative effects of marijuana on brain development are a cause for concern despite the limited research," the researchers say in urging doctors to counsel expectant mothers on marijuana use. According to one study they cite, THC is able to cross the placental barrier during gestation, which puts the fetus at risk for a variety of health complications, including preterm births or stillbirths. (The authors note the study was limited by the fact that mothers had to self-report their use and may not say whether they used other drugs.) While breastfeeding, new research published in Pediatrics shows traces of THC make their way into breastmilk, even days after pot use. "We still do not know whether the amount of THC that an infant receives through breastmilk is safe," Dr. Sheryl Ryan, of Penn State Health Milton S. Hershey Medical Center in Hershey, Pennsylvania, tells Reuters. "In the absence of safety data, we recommend abstaining—this is what should be of importance for breastfeeding women." The recommendations follow a study published in JAMA last year that found pot use has been on the rise among pregnant women in the past decade: In 2009, 4% of pregnant women in the United States used marijuana, which was up to 7% in 2016. The rise was largest among young women, with 22% of pregnant women under 18 and 19% of pregnant women aged 19-24 reporting pot use. During that same time period, pot has been legalized in more states. As Ryan adds, "There is a general feeling in the population that if it is legal, then it must be safe, which is a fallacy."