Marijuana use and morning sickness symptoms

An oral presentation at the Society for Maternal-Fetal Medicine’s (SMFM) 42nd Annual Pregnancy Meeting explored possible associations with marijuana use and nausea and vomiting in early pregnancy.¹

Cannabis use is increasing as many states legalize marijuana. Despite recommendations from the American College of Obstetrics and Gynecology, pregnant individuals frequently use marijuana to alleviate stress, anxiety, nausea, vomiting, and pain.² In a 2019 study, researchers conducted a test in which a “mystery caller” contacted 400 Colorado dispensaries to ask about morning sickness relief. Nearly 70% recommended cannabis use, despite a lack of scientific data.³

To further investigate the use of marijuana for morning sickness, Torri D. Metz, MD, MSCR, associate professor at the University of Utah Health in Salt Lake City, Utah, along with her co-authors, led an ancillary study to evaluate whether marijuana use was in fact associated with early pregnancy nausea and vomiting. Secondarily, they wanted to learn more about antiemetic use in individuals with and without marijuana use.⁴

The ancillary study used data from the prospective Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b), which recruited individuals from 2010 to 2013 from 8 US centers.

Metz and her team included only individuals who completed a Pregnancy-Unique Quantification of Emesis (PUQE) evaluation and consented to a frozen stored urine sample at the first study visit, which included 9,250 participants. Their primary outcome was the overall PUQE score, which involved 3 questions—how many hours in the past 12 hours have you felt nauseated? How many times in the past 12 hours have you vomited? How many times in the past 12 hours have you had retching or dry heaves?

Using the PUQE scores, they calculated nausea severity as mild, moderate, or severe—a PUQE score of 0 meant no nausea severity; A score of 1 to 6 was mild; 7 to 12 was moderate; and a score of 13 or more was qualified as severe. They also gathered antiemetic use via medical inventory that certified research staff collected at the time of the study.

Marijuana exposure was measured via biological sampling. Researchers did an immunoassay screen for 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC), followed by confirmatory testing with liquid chromatography-mass spectrometry with a cutoff at 15 ng/mL. They then quantified the THC in the urine and normalized it with urine creatinine. The team compared those with and without urine positive for THC. Multivariable logistic regression adjusted for maternal age, body mass index, prescription antiemetic use, and gestational age (P<0.05).

Researchers ultimately included 9,250 nuMoM2b participants in their analysis, 5.8% (95% CI 5.4-6.3%) of which were THC-positive (n=540). As for nausea severity, 46% (4,257) had no nausea symptoms; 38.2% (3,531) had mild nausea; and 15.8% (1,462) had moderate-to-severe nausea. The average gestational age at the first visit was between 11- and 12-week gestation.

THC-positive participants had higher rates of nausea symptoms, episodes of vomiting, and episodes of dry heaves than those who tested negative for THC (n=8,710). THC-positive participants, Metz said, were more likely to be younger, Black, live below the poverty line, and have public insurance. Interestingly, after multivariable modeling, incrementally higher THC was not significantly associated with any level of nausea (OR 1.6). 9.6% of participants reported using antiemetics at the first visit. THC-positive participants were more likely to report use of antiemetic (18 vs 12 with P<0.01).

The investigators concluded that, though they were unable to establish cause and effect through a retrospective study, they did find marijuana use to be associated with nausea and vomiting in early pregnancy. They also found that most THC-positive participants were taking only 1 antiemetic.

“Obstetricians should query about marijuana use,” Metz said, “to understand the reasons for use, and counsel [patients on] potential adverse effects. Nausea may be undertreated in early pregnancy, and we do have the opportunity to offer safe, effective alternatives.”

References

1. Metz T, Allshouse A, McMillin G, et al. Association of Marijuana Use with Nausea and Vomiting of Pregnancy. Oral concurrent session. SMFM Annual Meeting. February 3, 2022.
2. Ko JY, Coy KC, Haight SC, et al. Characteristics of Marijuana Use During Pregnancy — Eight States, Pregnancy Risk Assessment Monitoring System, 2017. MMWR Morbidity and Mortality Weekly Report. 2020;69(32):1058-1063. doi:10.15585/mmwr.mm6932a2
3. Dickson B, Mansfield C, Guiahi M, et al. Recommendations From Cannabis Dispensaries About First-Trimester Cannabis Use. Obstet Gynecol. 2018;131(6):1031-1038. doi:10.1097/AOG.0000000000002619
4. Metz TD, Allshouse AA, McMillin GA, Silver RM, Jarlenski MP. Association of Marijuana Use with Nausea and Vomiting of Pregnancy. American Journal of Obstetrics and Gynecology. 2022;226(1):S22-S23. doi:10.1016/j.ajog.2021.11.082