When women who are pregnant or breastfeeding use marijuana, does it harm their children?

Despite decades of research, experts say the answer is as murky as pot smoke. Studies of the effects of Cannabis sativa on fetal and child development are inconsistent, inconclusive, and insufficient.

But that uncertainty — plus the steamroller of state laws permitting marijuana use — has set up a deepening divide.

Medical, addiction, and law enforcement authorities say women should err on the side of caution and steer clear of marijuana.

Meanwhile, the growing ranks of mothers and mothers-to-be who swear by the plant to treat nausea, pain, migraines, depression, and more believe in erring on the side of women’s wisdom.

“We’re talking about women’s medical choices,” said Jeanna Hoch, 37, of Denver, founder of CannaMama Clinic, an online community that advocates cannabis use during pregnancy and lactation. “We are very firm in our beliefs about responsible consumption. We’re not just: ‘Hey, go get high when you’re pregnant and have a good time.' We just want the choice to use it medically.”

Research gaps grow

The health effects of marijuana in general are far from clear, a National Academies of Sciences, Engineering and Medicine review concluded in 2017.

Those research gaps are growing as the cannabis industry booms and innovates. Today’s varieties have been bred to have a higher concentration of tetrahydrocannabinol (THC) — the psychoactive compound that causes a high — than the cannabis of past generations. Cannabidiol (CBD), the component that doesn’t cause intoxication, is being touted as a miracle supplement for everything from acne to schizophrenia. And marijuana products now come in tablets, topicals, edibles, and vapes, as well as traditional smokable forms.

Despite the unknowns, 33 states, and counting, have legalized medical or recreational marijuana, or both. (Medical use is legal in Pennsylvania and New Jersey, and both states are debating full legalization.)

No states specifically allow medical marijuana for pregnancy-related conditions, but neither do they prohibit use or warn about possible harms to a fetus, according to the Prescription Drug Abuse Policy System.

“As a result, perceptions of cannabis safety have increased, and the prevalence of marijuana use among pregnant women has expanded,” Lauren M. Jansson, director of pediatrics at Johns Hopkins University’s Center for Addiction and Pregnancy, wrote last year in an opinion piece in JAMA.

While alcohol and tobacco use have been falling among pregnant women, the percentage who fessed up to marijuana use doubled between 2002 and 2014, to about 4 percent, federal surveys show. But the real prevalence is another unknown. Many moms keep mum because of stigma and fear of punishment. That fear is especially keen among women who have just given birth. Under federal and many state child abuse prevention laws, hospitals are supposed to notify child protective agencies about newborns who test positive for exposure to marijuana.

“At every hospital in Philadelphia, we say: ‘Do not use marijuana while you are pregnant or breastfeeding,' ” declares a flyer with the logos of five maternity hospitals, the city health department and the Maternity Care Coalition.

Pediatrician Steven A. Shapiro warns that marijuana exposure may harm babies' brains
Abington-Jefferson Health
Pediatrician Steven A. Shapiro warns that marijuana exposure may harm babies' brains

“If a baby has THC in the urine, we report the mom,” said Steven A. Shapiro, chair of pediatrics at Abington-Jefferson Health. “If you’re going to be pregnant, you shouldn’t be smoking marijuana.”

Hoch, in Denver, passionately disagrees. During both of her pregnancies, she told her obstetrician she was using marijuana to relieve severe morning sickness, or hyperemesis gravidarum, that didn’t respond to standard medication.

The birth of her daughter in 2014 — almost two years after Colorado voters passed an amendment legalizing marijuana — was the turning point in Hoch’s activism. The hospital drug-tested Hoch and her newborn, and a social worker repeatedly interviewed Hoch and her husband, making them feel “uncomfortable and threatened.”

“Mothers should not fear losing their children because they choose cannabis to treat their ailments,” said Hoch, who has spoken at scientific conferences on maternal marijuana use.

She sees her healthy, thriving children, ages 13 and 5, as evidence of the prudence of her choice.

“I know that’s anecdotal,” she said. “However, we believe that anecdotal evidence, when it mounts up, gives you a sense of reassurance to know how many women have found wellness through the plant.”

Anonymous testimonials abound online.

“I had morning sickness so bad and tried everything,” one woman wrote on the Cannavist Mom website. “A toke or two before getting out of bed helped tremendously. My daughter is now 20 and is as healthy as can be.”

“I am an educated, cannabis-loving mother to an extremely smart 3-year-old,” wrote another. “I started smoking around the age of 16 due to my major depression and anxiety. Pharmaceuticals made me sick. Smoking makes me a better mother.”

Theoretical risks

In the 1990s — long after THC and related compounds were isolated in cannabis – scientists discovered that the body produces its own cannabis-like substances. Humans, it turned out, have an intricate chemical messaging network, now called the endocannabinoid system.

That network, which is concentrated in the brain and nervous system, is involved in an array of critical neurological processes, from early brain development to thinking, mood, appetite, and pain sensation.

That’s why TCH is a particular concern. It readily crosses the placenta to the fetus, and small amounts get transferred via breast milk to a baby. In theory, this mind-altering chemical messenger could interfere with development.

Medical authorities often omit the “in theory” part.

“THC exposure can adversely affect fetal growth as well as structural and functional neurodevelopment,” Jansson, at Hopkins, declared in her opinion piece.

The Philadelphia hospitals’ poster, titled “Get the Facts,” says it more simply: “Marijuana can harm babies and their brains.”

A poster at five Philadelphia hospitals, titled “Get the Facts.”
Handout
A poster at five Philadelphia hospitals, titled “Get the Facts.”

There is no doubt that marijuana use can be harmful. A woman who compulsively abuses the drug has a recognized psychiatric illness called cannabis use disorder; it is bad for her and her offspring because, by definition, she suffers “significant impairment of functioning and distress.”

But the risks of more restrained use are tougher to assess. Since it would be unethical to test a potentially dangerous drug on pregnant or nursing mothers, researchers basically follow marijuana users and nonusers and look for differences in their kids. The results, which often rely on women’s not-so-reliable recollections, may be muddled in some cases by the effects of poverty, and the use of other drugs such as tobacco and alcohol.

The National Academies’ report devotes a whole chapter to a review of studies that looked for a link between marijuana use during pregnancy and bad outcomes, including miscarriage, stillbirth, fetal distress, fetal growth problems, premature birth, birth defects, and thinking and behavioral problems as late as adolescence.

The bottom line? Only one outcome – lower birth weight – was relatively strongly linked to smoking marijuana during pregnancy.

As for breastfeeding, there wasn’t even enough data to draw conclusions.

Nonetheless, expert groups, including the American College of Obstetrician-Gynecologists, the American Academy of Pediatrics, and the National Institute on Drug Abuse, say doctors and women should be worried, not reassured.

Because of concerns about brain development, as well as the ill effects of smoking, “women who are pregnant or contemplating pregnancy should be encouraged to discontinue marijuana use,” says the ob-gyns’ guidance.