More and more states are legalizing marijuana, but using it when you're expecting can be risky. Here's the latest on pot use for pregnant women.

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Warning labels on alcohol and cigarettes have long been in place, informing expectant women of the dangers of drinking and smoking. And in recent years, marijuana—the most commonly used illicit drug during pregnancy—joined this group of potentially harmful substances. Regulations from the American Medical Association (AMA), as outlined in resolution #922 (Cannabis Warnings for Pregnant and Breastfeeding Women), advocate for written warnings on medical and recreational marijuana products, as well as posted signage in establishments where they are sold.

"This resolution was introduced in part because the legalization of this substance is continuing and there are questions—and even misconceptions—about its safety during pregnancy. We want women to understand the risks involved," says Diana E. Ramos, M.D., MPH, a fellow of The American College of Obstetricians and Gynecologists (ACOG), an AMA delegate, and director of reproductive health at the County of Los Angeles Department of Public Health.

Risks of Smoking Pot While Pregnant

The risks of marijuana use during pregnancy are not as well documented as those related to alcohol or cigarette use, but they are not trifling.

Indeed, a December 2019 study from the University of Nevada, Las Vegas (published in the Journal of Maternal-Fetal and Neonatal Medicine) linked marijuana to an increased risk for delayed fetal growth. This has been associated with low birth weight, hypoglycemia, low Apgar scores, impaired resistance to infection, and other negative outcomes. In extreme cases, delayed fetal growth can cause stillbirth.

What's more, "smoking [marijuana] also makes it difficult for women to become pregnant and can harm the lungs, reducing the amount of oxygen a fetus receives during pregnancy," adds Linda Burke-Galloway, M.D., an OB-GYN in Orlando, Florida, and author of The Smart Mother's Guide to a Better Pregnancy.

The active ingredient in marijuana, THC (tetrahydrocannabinol), is capable of crossing the placenta, which means that the fetus could be exposed. In addition, it can also reach breast milk, a concern for women who nurse. "It's hard to fully understand the associated dangers, as some women who smoke it may also smoke cigarettes and/or drink. But because of the suggestion of a negative impact on the fetus, any use at all is simply not worth it," notes Dr. Ramos.

A Need for Regulations

With its proposal, the AMA is advocating for regulations that will evaluate marijuana products in much the same way as cigarettes and alcohol, says Jonathan Emery, M.D., assistant professor of surgery at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University and an OB-GYN at the Women's Health Institute. "While this language from the AMA doesn't appear to ask for an outright ban on the substance—the legalization of marijuana isn't decided at the federal level but rather by individual states—this push will help doctors and other health care providers to warn expectant mothers of the many risks to themselves and their babies if they choose to consume marijuana, legally or not."

According to ACOG's committee opinion, about half of female smokers continue to use marijuana when they're expecting. "We need to do a better job of reaching these women, and I believe this resolution would help us do so," Dr. Ramos says. With marijuana becoming more widely available than ever before, these proposed regulations may be extremely prescient. "This is a political question that's gaining momentum in many states, but it's important to remember that the risks of substance use and abuse in pregnancy can happen in all 50 states, regardless of the legal status of a particular drug," Dr. Emery adds.

The best advice for women is to safeguard their health before conception, during pregnancy, and when breastfeeding. "A healthy baby needs a healthy mother, so if you are planning to have a child, or you find out that you are pregnant, it's time to stop smoking, drinking, and using drugs," urges Dr. Ramos. Counseling, medication, and behavioral therapies may also be useful in some cases, Dr. Emery adds.