What the Research Says About Marijuana Use During Pregnancy

In recent years, the legalization of marijuana for recreational and medical use has made it easier to access. But just because marijuana is more widely legal and easier to get doesn’t mean it’s safe—especially during pregnancy.

Last year, the American College of Obstetricians and Gynecologists (ACOG) released new recommendations about marijuana use during pregnancy, strongly advising women against it. The updated guidelines were based on a review of multiple studies that found a strong link between marijuana use during pregnancy and problems like pre-term birth, low birth weight and even infant death.

How Does Marijuana Hurt a Fetus?

The placenta grows in a woman’s uterus during pregnancy. It delivers oxygen and essential nutrients to the fetus, like glucose, amino acids, fatty acids and minerals, through the umbilical cord.

“Recent research suggests marijuana can decrease blood flow and oxygen in the placenta,” says Jonathan Fanaroff, MD, JD, a neonatologist at University Hospitals Rainbow Babies & Children’s. “When the placenta cannot deliver enough oxygen and nutrients, the fetus may not grow properly and have a low birth weight.”

It’s been proven that tetrahydrocannabinol (THC), the psychoactive compound in marijuana, crosses the placenta and accumulates in the fetus’s brain and other tissues.

“Pregnant women who use marijuana may increase their child’s risk of experiencing attention deficit disorder and other behavioral issues during childhood and adolescence,” Dr. Fanaroff says. He adds that more research is still needed to fully understand these effects.

More Pregnant Women Are Using Marijuana

The number of pregnant women using marijuana is on the rise as more states legalize the drug. Studies suggest this may be happening because some women are unsure about the risks, given the reported health benefits of marijuana, which include relieving chronic pain, chemotherapy-induced nausea, muscle spasms, and mental health conditions such as anxiety and PTSD.

More women are turning to marijuana-based products to help with morning sickness, anxiety and trouble sleeping during pregnancy.

What About CBD?

Cannabidiol (CBD) is an oil obtained from the cannabis plant that does not contain significant levels of THC. Sold as a gel cap, gummy or liquid in a wide range of doses, CBD doesn’t alter the mind or cause a “high.” By law, CBD may have up to 0.3 percent THC based on how it is extracted and purified. Many people report that over-the-counter CBD products help relieve chronic pain, anxiety, sleep problems and PTSD.

CBD is widely considered a safe, non-intoxicating alternative to THC. However, until the effects of using CBD during pregnancy are better understood, both the ACOG and U.S. Food and Drug Administration advise pregnant women against using it.

Research Is Ongoing

Older studies, many done in the 1980s, didn’t find a strong link between marijuana use during pregnancy and problems with fetal development. One reason for this may be that marijuana was much less potent at the time.

“On average, the marijuana available in the 1980s had less than 5% THC and included a mix of leaves, stems and buds,” says Dr. Fanaroff. “Modern marijuana farming uses growing practices that can increase THC levels over 20%.”

Are Edibles Safer Than Smoking Marijuana?

Edibles — such as THC-containing gummies, brownies and drinks — have become more popular in recent years. However, while edibles don’t harm the lungs like smoking does, they have their own health risks. For example, people may accidentally take too much.

“Whether a pregnant mother smokes or eats marijuana, THC still passes through the placenta to the fetus,” says Dr. Fanaroff. “The American College of Obstetricians and Gynecologists advises pregnant and breastfeeding women against any form of cannabis. Also, ‘medical marijuana’ carries the same risks as recreational marijuana.”

Better Education and Public Messaging

Dr. Fanaroff says that as marijuana use continues to grow and more people underestimate the harm it may cause, education will become even more important.

“Honest, non-judgmental conversations about the known and unknown risks to the fetus can help families better understand the potential dangers of using marijuana during pregnancy.”

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For nearly 100 years, leading neonatal researchers and pediatric specialists at UH Rainbow Babies & Children’s Hospital have led the efforts to develop and advance newborn care.