Marijuana Use Jumps in Pregnant Women

Pam Harrison

December 29, 2016

Marijuana use by pregnant women in the United States jumped by 62% between 2002 and 2014, and experts worry that its use will lead to adverse outcomes in both mothers and their infants, an analysis of the National Survey on Drug Use and Health indicates.

"Among all pregnant women, the adjusted prevalence of past-month marijuana use increased from 2002 to 2014," lead author Qiana Brown, PhD, Columbia University, New York City, and colleagues report.

Young women between the ages of 18 and 25 were the most likely to report past-month use of marijuana, at 7.47%, in 2014, they add. Of the 200,510 women analyzed during the study period, almost 30% were between 18 and 25 years of age.

In contrast, the prevalence of past-month marijuana use was only 2.12% in women aged 26 to 44 years. The difference between the age groups was statistically significant (P = .02).

"Past-year use was higher overall, reaching 2014, with similar trends over time," the investigators write.

The findings were published online December 19 in JAMA.

Bad Advice

Among women who were not pregnant at the time of the analysis, the investigators found that 9.27% reported using marijuana in the past month and that 15.93% reported using marijuana in the past year.

In an accompanying editorial, Nora Volkow, MD, Wilson Compton, MD, and Eric Wargo, PhD, all with the National Institute on Drug Abuse in Bethesda, Maryland, warn that some Internet sites are advertising the use of marijuana as a treatment for nausea that often accompanies pregnancy, especially during the first trimester.

"Of course we're concerned about these sites, but we're not at all surprised by them, because the marijuana business is going to use tactics used by businesses everywhere to increase the likelihood that you will consume their product," Dr Volkow told Medscape Medical News.

"And because marijuana actually is effective for nausea, you can put two and two together and see why these sites are saying, instead of taking a drug, use a plant to relieve the nausea," she added.

Putting a policy into place that ensures there is no advertising of marijuana for use during pregnancy will be an important public health message, Dr Volkow noted.

There are substantial theoretical reasons for concern that marijuana use during pregnancy could harm fetal neurodevelopment.

"Data derived from animal studies and basic research recognize that the endogenous endocannabinoid system, which is stimulated by marijuana, appears very early on during fetal development," said Dr Volkow.

This system is fundamental for brain processes related to neuronal cell proliferation, neuronal migration, and synaptic formation, she added.

Brain Architecture Disruption

In animal experiments in which researchers used tetrahydrocannabinol (THC), the main psychoactive ingredient in marijuana, as well as other cannabinoids, results showed that there was significant disruption in the ultimate architecture of the brain.

"We need to interpret these animal experiments with caution because the doses used in these experiments were higher than those that people consume," Dr Volkow observed.

"But I do believe that there are adverse effects from the use of marijuana during fetal development because of the extremely important role that the endogenous endocannabinoid system plays in fetal neurodevelopment," Dr Volkow said.

"I would advise physicians to talk to their patients regardless of whether they are pregnant or are thinking about getting pregnant not to consume marijuana for either medical or recreational purposes during pregnancy because, even though we don't know that much about the negative effects it might have, there is sufficient evidence to indicate that it could be potentially harmful to the fetus, and that will translate into adverse outcomes for the newborn."

A systematic review and meta-analysis of the available evidence conducted by investigators at the University of Arizona in Tucson revealed that women who used marijuana during pregnancy were more likely to be anemic than nonusers.

Pre- and Postpregnancy Use Inadvisable

Infants exposed to cannabis in utero were also more likely to be of low birth weight at birth and to require neonatal intensive care compared to infants born to mothers who did not use marijuana during pregnancy.

However, the investigators note that these findings may well have been confounded by concurrent use of alcohol, tobacco, or both during pregnancy and that they may not be the result of marijuana alone.

"The fact that there isn't a whole lot of research on this topic means the effects of marijuana use in pregnancy are really unknown at this point in time," lead author Jaylee Gunn, PhD, told Medscape Medical News.

"And while I am not a physician, I would suggest they simply be honest with women and tell them that effects of marijuana on fetal development are not known right now, so there is no way of telling what their outcomes might be."

The American College of Obstetricians and Gynecologists issued a committee opinion in 2015 discouraging pregnant and lactating women from using marijuana even preconceptually.

The authors, editorialists, and Dr Gunn report no relevant financial relationships.

JAMA. Published online December 19, 2016. Full text, Editorial


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