Study Finds Marked Increase in Marijuana Use among Pregnant Women

By Melissa Moore
Monday, May 1, 2017

Use of marijuana by expectant mothers in the United States rose 62 percent from 2002 through 2014, raising concerns among researchers even as legalization of pot has spread.

About one in 20 women uses some form of traditionally illicit drug during pregnancy, and they are more likely to use marijuana than drugs such as cocaine or heroin.

A recent analysis of the National Survey on Drug Use and Health found that from 2002 through 2014, the number of pregnant women who said they had used marijuana in the past month increased from 2.37 percent to 3.85 percent. At 7.47 percent, women between the ages of 18 and 25 were the most likely to have smoked pot in the past month, according to the study, which was published in JAMA.

During roughly the same period, marijuana use has risen in the general population as well, with use among adults doubling between 2001 and 2013 and many states legalizing the drug.

Behind the Trend

The upward trend in prenatal marijuana use is likely driven by multiple, interconnected factors, according to Qiana L. Brown, PhD, MPH, LCSW, postdoctoral research fellow at the Mailman School of Public Health at Columbia University and lead author of the study.

“These include individual-level factors, such as knowledge of health risk associated with prenatal marijuana use, and socioenvironmental factors, such as the fact that more than half of American states have legalized marijuana use for medical or recreational purposes,” Brown says.

In addition to lack of awareness about marijuana’s risks and increasingly permissive attitudes toward the drug, some pregnant women may seek out marijuana during pregnancy to alleviate symptoms of nausea, notes an editorial accompanying the JAMA study.

“The idea of using marijuana to treat their nausea probably seems logical to many pregnant women, especially if they live in states that have legalized recreational or medical marijuana,” says Nora Volkow, MD, Director of the National Institute on Drug Abuse and lead author of the editorial. “Marijuana does have anti-nausea properties ... [and] many pregnant women may be searching for a ‘natural’ herbal alternative to prescribed medications. ... Unfortunately, because of marijuana’s potential effects on fetal development, there could be consequences for the child that the mother does not anticipate.”

Risks and Recommendations

“The potential impact of marijuana exposure on prenatal brain development is supported by our understanding that the endocannabinoid system — the system of receptors on neurons that tetrahydrocannabinol interacts with — plays a key role in the early developing brain, helping new neurons migrate to their correct position in the brain and helping their axons make the necessary connection to other neurons,” Dr. Volkow says. “Thus, any external chemical that interacts with this system would be expected to have detrimental effects that could be long-lasting.”

“There is enough data showing adverse effects, as well as the theoretical rationale from our understanding of the role played by the endocannabinoid system in prenatal brain development, to justify great caution around this drug during pregnancy.”
— Nora Volkow, MD, Director of the National Institute on Drug Abuse

There are other medical concerns as well. A meta-analysis published in BMJ Open found that in current literature, anemia was the most widely noted consequence of marijuana use for expectant mothers. The study also found infants who were exposed to cannabis in the womb had decreased birth weight and were more likely to need intensive care compared with infants who were not exposed. Isolating the effect of marijuana is a challenge, however.

“As the use of cannabis gains social and medical acceptance, understanding its effects on maternal and fetal outcomes remains essential,” authors of the study write. “There remains a gap in the literature assessing the effects of cannabis excluding other illicit drug use. As many cannabis users are often tobacco or alcohol users, determining a cannabis-only effect was currently not possible.”

Although research is ongoing, the fetal and child health risk associated with prenatal marijuana use led the American College of Obstetricians and Gynecologists (ACOG) to recommend that physicians refrain from prescribing or suggesting marijuana for medical purposes during preconception, pregnancy and lactation. Women with medical needs addressed by marijuana should be counseled about other treatment options that present less risk for mother and baby. Furthermore, ACOG urges physicians to ask pregnant women and women contemplating pregnancy if they use illicit or recreational drugs and provide resources to help them avoid using these substances during pregnancy.

Brown agrees with these recommendations, encouraging physicians to use their influence to protect the health of their patients.

“Physicians can be key change agents in treating and preventing substance use during pregnancy,” Brown says. “Although some people can use marijuana without harm, prenatal marijuana use should be viewed as a separate public health and medical concern, considering its potential risk to both maternal and child health.”