Marijuana may be losing its image as a dangerous drug, but mounting research suggests women should steer clear of it if they are pregnant or breastfeeding, according to new recommendations from the American Academy of Pediatrics.
The advice comes as more than half of the states, including California, have legalized marijuana for medical or recreational use. Growing acceptance of the drug has made it seem harmless, or even beneficial. As a result, doctors fret that more and more babies are being exposed to the drug.
The march toward legalization has outpaced scientific research about marijuana’s health effects. Because it is a Schedule 1 drug — one with potential for abuse and no approved medical use — studies have been limited by federal law.
But in a detailed review of existing safety data, researchers cited concerns about marijuana’s effect on children’s short-term growth and long-term neurological development. Their findings were published Monday in the journal Pediatrics.
“Women should definitely be counseled that it’s not a good idea to use marijuana while pregnant,” said Dr. Seth Ammerman, a clinical professor of pediatrics at Stanford who worked on the report.
In addition, he said, “if you’re breastfeeding, we would encourage you to cut back or quit.” However, if a new mother is not able or willing to do so, she should continue nursing. “The benefits of breastfeeding would outweigh the potential exposure to the infant,” he said.
A second report, also published in Pediatrics, found that THC, the molecule responsible for most of marijuana’s psychoactive effects, accumulates in breast milk for up to six days after the mother’s last use.
The findings come as marijuana use among pregnant women is rising. Data from the National Survey on Drug Use and Health show that the proportion of pregnant women who said they used marijuana in the past month increased from 2.4% in 2002 to 3.9% in 2014, according to a study in the Journal of the American Medical Assn. A separate JAMA report of pregnant women treated at Kaiser Permanente medical offices in Northern California found that marijuana use by pregnant women jumped from 4% in 2009 to 7% in 2016.
In studies of urban, young and socioeconomically disadvantaged pregnant women, 15% to 28% reported using the drug, according to the American College of Obstetricians and Gynecologists.
Unlike for alcohol and cigarettes, marijuana may not carry a safety warning for pregnant women, even when it is sold legally. California requires safety warnings, but many other states do not.
“There’s a myth out there that it’s benign. And for many adults who are sporadic users, that’s probably true,” Ammerman said. But when it’s used by women who are pregnant or nursing, “it may be harmful.”
Of particular concern, he said, is that the potency of THC in marijuana has more than quadrupled since 1983. Several of the largest studies on marijuana and health were conducted when potency was much lower, according to the academy’s new report.
Scientists have found that THC can cross the placenta and accumulate in the brain and fat of a growing fetus. The limited studies available suggest that prenatal exposure to marijuana could interfere with children’s executive functioning, causing problems with concentration, attention, impulse control and problem-solving.
Nonetheless, online mothers groups are filled with women touting the benefits of using marijuana during pregnancy, citing the drug as a remedy for the nausea of morning sickness.
Cannabis dispensaries are another source of dubious information. A study in the American Journal of Obstetrics and Gynecology, for example, found that nearly 70% of dispensaries in Colorado recommended marijuana to treat morning sickness during the first trimester despite a lack of evidence that marijuana use is safe or indicated for morning sickness. The worst nausea occurs during the first trimester, when the developing fetus might be most vulnerable to the effects of substances like THC.
“As health professionals, we need to educate women that there are a lot of concerns both for the fetus and for later development,” said Kelly Young-Wolff, a research scientist at the Kaiser Permanente Northern California Division of Research, who was not involved in the new Pediatrics reports.
But convincing women of the dangers of cannabis use during pregnancy can be challenging — especially when they’ve already decided that using it is safe.
On Facebook, the group “Stoner Moms” has more than 22,000 followers. And the Glow Nurture pregnancy app has several community groups devoted to marijuana users, including “420 Friendly,” “Ganja Mommies” and “CannaMoms.”
The conversations are filled with women asking not whether marijuana could be harmful, but whether smoking it could lead to a visit from Child Protective Services.
“A lot of the public equates legalization with some kind of endorsement of safety,” said Dr. Dana Gossett, a professor of obstetrics and gynecology at UC San Francisco. “Of course, that’s not true.”
When she counsels patients to avoid marijuana, Gossett said, she runs into a “fair amount of indifference.”
Pregnancy is often a time when women are receptive to changing their habits for the sake of their growing baby. But while they generally accept that cigarette smoking is dangerous — that’s been clear since the 1960s — they often view marijuana as natural, and therefore harmless.
“Just because something is plant-based or natural doesn’t make it safe,” Gossett said. Arsenic, she added, is also a natural substance.