According to research published in the Journal of the American Medical Association, there has been a significant increase in the use of marijuana among pregnant women over the last decade.  Among all pregnant women, the prevalence of marijuana use (assessed in the past month) increased from 2.37%  in 2002 to 3.85% in 2014 (prevalence ratio [PR], 1.62 [95% CI, 1.09-2.43]). Marijuana use was the highest in women aged 18 to 25 years, with past-month prevalence reaching 7.47% in 2014.

The data reflect an overall increase in the use of marijuana among Americans.  Over the last decade, marijuana use among US adults has more than doubled, as many states have legalized marijuana use and attitudes toward marijuana became more permissive.

But just because it is legal or can be medically prescribed doesn’t mean that it is safe.

While marijuana is often considered to be a relatively benign substance, we have data to indicate that the developing fetus may be particularly vulnerable to its effects.  Preliminary data indicating a spectrum of risks to the fetus related to maternal marijuana use, including increased risk of intrauterine growth restriction, low birth weight, stillbirth, and cognitive delays and deficits, poor executive functioning.  (We have reviewed these findings in previous posts here and here.) 

Also concerning is that a growing number of people who view marijuana as a safer or more effective option than traditional pharmacologic interventions for the treatment of a variety of conditions, including nausea and vomiting, depression, and anxiety.  At this point, there is no data to support the use of marijuana for the management of these symptoms.  (This review published in JAMA reviews clinical studies using marijuana.)  ACOG recommends that pregnant women or women contemplating pregnancy should be counseled  to discontinue use of marijuana for medicinal purposes in favor of an alternative therapy for which there are better data regarding reproductive safety.  Reflecting these concerns, the American College of Obstetricians and Gynecologists (ACOG) has issued a committee opinion on the use of marijuana in pregnant and nursing women, calling for ob-gyns to urge their patients who are pregnant or contemplating pregnancy to discontinue marijuana use.

It should also be noted that, even in states where marijuana is legalized, pregnant women who use marijuana may be viewed differently than users who are not pregnant.  In Colorado, where both medical and recreational marijuana are legal, the Department of Public Health & Environment advises women not to use marijuana during pregnancy. Furthermore, if the baby tests positive for THC (the active ingredient of marijuana) at birth, the law requires notification of child protective services.  (Apparently this may occur even if the marijuana is medically prescribed.)  With the legalization of recreational marijuana in Massachusetts last week, we have yet to see how these issues will play out in our obstetric population.     

Ruta Nonacs, MD PhD


Brown QL, et al. Trends in Marijuana Use Among Pregnant and Nonpregnant Reproductive-Aged Women, 2002-2014.  JAMA. Published online December 19, 2016.


Read More:

Recent Pot Use in Pregnancy Has Become More Prevalent (MedPage Today)

Pot And Pregnancy: No Harm Seen At Birth, But Many Questions Remain (NPR)



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