Marijuana During Pregnancy: How Should Physicians Advise Pregnant Women?

As some states have legalized marijuana in recent years, for medical use and/or recreational use, the use of marijuana during pregnancy has also increased; almost 4% of pregnant women said they had used marijuana in the past month in 2014, compared with 2.4% in 2002, according to a recent study published in the Journal of the American Medical Association.

The New York Times recently highlighted the stories of several women who had written in about their experiences taking the drug while they were pregnant; of the “hundreds” of readers who wrote in, “most had smoked, while a few vaped or ate marijuana-laced edibles,” the article says. “Roughly half said they had used pot for a medical reason,” such as nausea or back pain.

“Most felt marijuana use had not affected their children, or were not sure; just a handful worried the children might have suffered cognitive deficits.”

However, the acceptance of marijuana has “outstripped scientific understanding of its effects on human health…Often pregnant women presume that cannabis has no consequences for developing infants. But preliminary research suggests otherwise.”

Indeed, “cannabinoids readily cross the placenta, entering the fetal circulation and brain, and higher fetal levels are seen with chronic use,” Jennifer Gunter, MD, an ob/gyn, points out in a June 2017 commentary.

“Another concern is that doses of THC [tetrahydrocannabinol, the main psychoactive ingredient] in marijuana have increased dramatically, from 4% in 1995 to 12% in 2014, with labs in Colorado reporting THC concentrations in some strains as high as 30%,” Gunter says. “Women choosing to use marijuana in pregnancy will be exposed to significantly higher doses compared with 20 years ago.” Also, “many strains that claim to be high in CBD [cannabidiol, the ingredient that may help nausea and pain] in fact contain little, if any.”

As for the various ways in which marijuana may be taken, “while women may think that marijuana concentrates and edibles are healthier because they do not involve smoking, they can still have significant and potentially harmful solvent residue from processing with chemicals such as butane,” she says.

“The endocannabinoid system is complex and not fully understood,” Dr. Gunter points out. “Animal studies show that prenatal exposure to THC, even at low doses, causes long-lasting neurologic changes among exposed progeny.” And in a recent meta-analysis of 24 studies of sufficient quality, women who use cannabis during pregnancy were found to have an “increased risk for anemia.” That study also found that “fetal exposure reduces birth weight and increases the need for neonatal intensive care unit admission.”

The American College of Obstetricians and Gynecologists (ACOG) recommends asking all women about marijuana use, Gunter notes. “Given the unsubstantiated reports of safety that women may find online, prenatal providers should be prepared to provide clear information about the safety concerns in a nonjudgmental way. It’s important that women get this information from their health providers so that they have accurate data to inform their medical decision-making. Prenatal providers should encourage women to report nausea and vomiting early and not downplay symptoms, as lack of help from traditional medicine may be one reason that women turn to marijuana.”

Gunter notes that ACOG “specifically recommends against advising marijuana use for nausea and vomiting in pregnancy. ACOG also recommends that providers help women who are using marijuana for medical reasons to find alternatives with pregnancy safety data.”

“Discussions about marijuana can be hard as the ‘safety’ of the drug seems entrenched,” she notes. “But I’ve found that many patients are receptive when I explain to them the extremely high concentrations of THC in modern strains, the often low levels of CBD despite advertising to the contrary, and concerns about solvents.”

This discussion highlights the fact that while some patients may assume that marijuana is safe and effective, and the main ob/gyn association recommends its members point patients toward prescription alternatives, the truth is we simply don’t know whether marijuana is safe or effective for pregnant women to treat symptoms such as nausea and pain.

This is yet another example of where data is lacking. What should physicians do in any situation in which there is insufficient data to make a recommendation? The answer as I see it: Admit researchers don’t have the answer yet. Although I realize this may be uncomfortable for many docs, it’s ok to say, “I don’t know.”

What the evidence suggests so far is the potential for cannabinoids to affect the brain and circulatory system of the baby in the womb. Thus, pointing out the potential risks of marijuana use during pregnancy, as noted by Dr. Gunter above, while acknowledging the overall lack of conclusive data, would seem the appropriate approach.