Maternal Cannabis Use During Pregnancy Associated With Adverse Health Outcomes


A recent study found that cannabis exposure over the course a pregnancy was associated with small-for-gestational-age birth, medically indicated preterm birth, stillbirth, or hypertensive disorders of pregnancy.

Exposure to cannabis during pregnancy is associated with several unhealthy outcomes that are related to placental function, according to new research published in JAMA Network Open.1 The findings suggest that cannabis use should be avoided during pregnancy.

Cannabis is the most commonly used federally illegal drug in the United States, according to the CDC. Use of the drug has been increasing in recent years as more states legalize recreational and medical use. However, a complete understanding of how cannabis impacts health is not known.

“There’s so much information out there—discussion and social media channels and on the Internet—about cannabis use and pregnancy,” Torri Metz, MD, lead author on the study, said in a release.2 “I think it’s hard for patients to understand what they should be worried about, if anything.”

Investigators from the University of Utah Health conducted an observational cohort study to evaluate the association between maternal cannabis use and adverse pregnancy outcomes known to be related to placental function. Data was gathered from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-B, which studied pregnant women delivering for the first time across 8 medical centers in the US from 2010 through 2013.

The study cohort included 9257 participants. Investigators tested stored frozen urine samples for 11-nor-9-carboxy-Δ9-tetrahydrocannabinol to determine cannabis exposure. Samples were taken during gestational age windows of 6 weeks to 13 weeks and 6 days; 16 weeks to 21 weeks and 6 days; and 22 weeks to 29 weeks and 6 days.

The primary study outcome was a composite adverse pregnancy outcome, which included small-for-gestational-age birth, medically indicated preterm birth, stillbirth, or hypertensive disorders of pregnancy.

Investigators found that of the 610 participants with cannabis use, 197 had exposure during only the first trimester and 413 had ongoing exposure. The composite adverse pregnancy outcome was more frequent in pregnant individuals with cannabis exposure when compared to those with no exposure (25.9% vs. 17.4%).

Additionally, although cannabis exposure during only the first trimester was not associated with the composite adverse pregnancy outcome, exposure over the course an entire pregnancy was associated with a higher risk for unhealthy outcomes.

“Cannabis use is not safe,” Robert Silver, MD, an author on the study, said in a release.2 “It increases the risk of pregnancy complications. If possible, you shouldn’t use cannabis during pregnancy.”

“There are many, many reasons people use cannabis,” Silver added. “But there may be alternative therapies that can help mitigate the symptoms.”

1. Metz TD, Allshouse AA, McMillin GA, et al. Cannabis Exposure and Adverse Pregnancy Outcomes Related to Placental Function. JAMA. 2023;330(22):2191–2199. doi:10.1001/jama.2023.21146.
2. Cannabis exposure linked to 1.5 times higher risk of unhealthy pregnancy outcomes. News release. University of Utah Health. December 12, 2023. Accessed December 12, 2023.
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