With marijuana legal in Oregon, more mothers-to-be are asking about the risks pot may pose, according to Cheryl Lugenbill, MD, medical director of Women’s and Children’s Services at Salem Health.

Her advice? If you’re pregnant or breast-feeding, don’t use marijuana.

“We see many patients who admit to using marijuana in pregnancy,” she said. “Even though they’re hopefully counseled by their prenatal providers, my impression is that patients tend to downplay the risks in general. Little is known about ‘safe limits,’ so our advice is not to use it.”

Clinicians share information with families that marijuana, along with other substances such as alcohol, is not safe for pregnant moms or breast-feeding babies, she said. They encourage mothers who are using medical marijuana to talk with their provider about safer choices that don’t harm the baby.

Salem Health follows recommendations from the American College of Obstetricians and Gynecologists. In a 2015 position paper, the ACOG discouraged the use of marijuana during pregnancy, noting it was the most commonly used drug during pregnancy (from two to five percent of pregnant women using it).

“Because of concerns regarding impaired neurodevelopment, as well as maternal and fetal exposure to the adverse effects of smoking, women who are pregnant or contemplating pregnancy should be encouraged to discontinue marijuana use,” it states. “Obstetrician–gynecologists should be discouraged from prescribing or suggesting the use of marijuana for medicinal purposes during preconception, pregnancy, and lactation.”

ACOG also discourages use because there is insufficient data to evaluate the effects of marijuana use on infants during lactation and breast-feeding.

However, the report did note fetal brain development, including neurotransmitter systems, can be affected as early as 14 weeks of gestation, with increasing receptor density as the fetus grows. And, marijuana smoke contains many of the same respiratory disease-causing and carcinogenic toxins as tobacco smoke, often in concentrations several times greater than in tobacco smoke.

What about just breastfeeding? There’s insufficient data to evaluate the effects of marijuana on infants during lactation, so in the absence of data, clinicians discourage it. High-quality studies about marijuana use during pregnancy and breast-feeding are needed before any further opinions are issued.

All very good reasons to think twice about using marijuana if you’re pregnant or breast-feeding. The full position paper can be found here.