Nausea and vomiting of pregnancy and prenatal cannabis use in a Michigan sample

Background: Nausea and vomiting of pregnancy, also referred to as morning sickness, affects more than 70% of all pregnancies. Symptoms range from mild to severe and, in some cases, can be debilitating, resulting in a reduced quality of life. Moreover, prenatal cannabis use prevalence has doubled in the United States, and cannabis potency, measured by the concentration of delta-9-tetrahydrocannabiniol, has increased from 10% in 2009 to 14% in 2019. State-level recreational legalization of cannabis may contribute to the liberalization of its use and reduced risk perception. Furthermore, the relatively recent discovery of cannabinoid hyperemesis syndrome may contribute to the mischaracterization of morning sickness in individuals who use cannabis during pregnancy. Although cannabis has well-documented antiemetic properties, there is insufficient research on the topic. Therefore, it is essential to establish a tangible understanding of the association between nausea and vomiting of pregnancy and prenatal cannabis use.

Objective: This study aimed to estimate the degree to which nausea and vomiting of pregnancy might be associated with prenatal cannabis use in a sample of pregnant people in Michigan, a state where recreational cannabis use became legal in December 2018.

Study design: This was a prospective study of participants from the Michigan Archive for Research on Child Health, a population-based pregnancy cohort that was recruited using a probability-based sampling approach. Participants were recruited from 22 prenatal clinics located throughout Michigan's lower peninsula. Cross-sectional analyses were performed for data available between October 2017 and January 2022.

Results: Among this sample of Michigan pregnant people, 14% (95% confidence interval, 11%-16%) reported cannabis use. Participants who experienced increasing morning sickness severity had higher odds of using cannabis (adjust odds ratio, 1.2; 95% confidence interval, 1.1-1.2). When the sample was restricted to first-trimester morning sickness and cannabis use, the results remained statistically robust. When the direction of the association was reversed, an increase in morning sickness severity was detected among participants who used cannabis during pregnancy (ß_adjusted, 0.2; 95% confidence interval, 0.1-0.2). Lastly, the association between prepregnancy cannabis use and first-trimester morning sickness was investigated. Study findings suggest an increase in morning sickness severity among people who used cannabis in the 3 months before pregnancy compared with those who did not use cannabis (ß_adjusted, 0.1; 95% confidence interval, 0.003-0.200).

Conclusion: Study findings indicated a link between nausea and vomiting of pregnancy and prenatal cannabis use. Moreover, this study revealed that using cannabis in the 3 months before pregnancy is associated with first-trimester morning sickness severity. The strengths of our study contribute to the scant epidemiologic evidence in this area of research. More fine-grained, time-specific data on nausea and vomiting of pregnancy and prenatal cannabis use are necessary to draw inferences about cause-effect relationships. Our study might provide a basis to discourage cannabis use during pregnancy until more evidence is collected.