Protection Versus Progress: The Challenge of Research on Cannabis Use During Pregnancy

Prenatal Cannabis Use and Maternal Pregnancy Outcomes

Importance

Many studies have evaluated whether in utero cannabis exposure is associated with fetal and neonatal outcomes, yet little is known about whether prenatal cannabis use is associated with maternal health outcomes during pregnancy.

Objective

To evaluate whether prenatal cannabis use is associated with maternal health outcomes during pregnancy.

Design, Setting, and Participants

This population-based retrospective cohort study included pregnancies in Northern California from January 2011 to December 2019 that lasted 20 weeks or longer and were screened for prenatal cannabis use.

Exposures

Prenatal cannabis use was defined as any self-reported use during early pregnancy or a positive toxicology test result based on universal screening at entrance to prenatal care (approximately 8-10 weeks' gestation). Self-reported frequency of use (daily, weekly, monthly or less, never, unknown), use defined only by self-report, and use defined only by toxicology test results were examined.

Main Outcomes and Measures

Electronic health record data were used to define the following outcomes: gestational hypertension, preeclampsia, eclampsia, gestational diabetes, gestational weight gain greater and less than guidelines, placenta previa, placental abruption, placenta accreta, and severe maternal morbidity. Adjusted risk ratios (aRRs) were calculated using a modified Poisson regression.

Results

The sample (n = 316 722 pregnancies; 250 221 unique individuals) included 84 039 (26.5%) Asian/Pacific Islander, 20 053 (6.3%) Black, 83 145 (26.3%) Hispanic, and 118 333 (37.4%) White individuals; the mean (SD) age was 30.6 (5.4) years. Overall, 20 053 (6.3%) screened positive for prenatal cannabis use; 2.9% were positive by self-report, 5.3% by toxicology testing, and 1.8% by both. The frequency of cannabis use was 1930 (0.6%) daily, 2345 (0.7%) weekly, 4892 (1.5%) monthly or less, and 10 886 (3.4%) unknown. Prenatal cannabis use was associated with greater risk of gestational hypertension (aRR, 1.17; 95% CI, 1.13-1.21), preeclampsia (aRR, 1.08; 95% CI, 1.01-1.15), weight gain less than (aRR, 1.05; 95% CI, 1.01-1.08) and greater than (aRR, 1.09; 95% CI, 1.08-1.10) guidelines, and placental abruption (aRR, 1.19; 95% CI, 1.05-1.36). The pattern of results was similar when defining prenatal cannabis use only by self-report or only by toxicology testing, and associations between the frequency of prenatal cannabis use and outcomes varied with outcome.

Conclusions and Relevance

The results of this cohort study suggest that prenatal cannabis use was associated with several adverse maternal health outcomes during pregnancy. Continued research is needed to understand whether characteristics of prenatal cannabis use (eg, dose, mode, and timing) moderate these associations.

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 (ßadjusted, 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 (ßadjusted, 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.