Maternal cannabis use linked to adverse pregnancy outcomes related to placental function

Key takeaways:

• Two-thirds of women who used cannabis during pregnancy did so beyond the first trimester.
• Ongoing use was linked to slow fetal growth, preterm birth, stillbirth and hypertensive disorders of pregnancy.

Maternal cannabis use was associated with adverse pregnancy outcomes, including small for gestational age, preterm birth, stillbirth and hypertensive disorders of pregnancy, linked to placental function, researchers reported in JAMA.

“Prior data are limited by confounding because the group of individuals that uses cannabis during pregnancy differs from those who do not use cannabis during pregnancy by a number of characteristics, including nicotine use, that may influence pregnancy outcomes,” Torri D. Metz, MD, MS, associate professor of obstetrics and gynecology, maternal-fetal medicine subspecialist and vice chair of Research of Obstetrics and Gynecology at the University of Utah Health, and colleagues wrote. “In addition, there are medical conditions, such as anxiety and depression, for which pregnant people may use cannabis; these conditions may also independently affect pregnancy outcomes.”

Metz and colleagues conducted an ancillary analysis of data from 9,257 women from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be, a multicenter cohort study of 10,038 women who were treated at eight U.S. medical centers from 2010 to 2013. All participants in this analysis had stored urine samples and abstracted pregnancy outcome data.

Researchers identified cannabis exposure through urine immunoassay using frozen stored urine samples from study visits that occurred during pregnancy, and positive results were confirmed with liquid chromatography tandem mass spectrometry.

The primary composite outcome included small for gestational age birth, preterm birth, stillbirth or hypertensive disorders of pregnancy.

Overall, 6.6% of women had cannabis use during pregnancy. Of those, 32.4% used cannabis only during the first trimester and 67.6% had ongoing exposure beyond the first trimester.

In propensity score-weighted analyses adjusted for sociodemographic information, BMI, medical comorbidities and active nicotine use, cannabis exposure during any time in pregnancy was associated with the primary composite outcome (25.9% vs. 17.4%; adjusted RR = 1.27; 95% CI, 1.07-1.49). When assessing no cannabis exposure, exposure during the first trimester only or ongoing exposure, researchers observed no association between cannabis use during the first trimester and the primary composite outcome. However, ongoing cannabis use was associated with the primary composite outcome (aRR = 1.32; 95% CI, 1.09-1.6).

“Further evaluation in humans of modes of cannabis consumption that do not require inhalation and frequent co-use or contamination with nicotine products may help provide further insight into the relationship between cannabis, nicotine and fetal growth,” the researchers wrote.