Marijuana use and pregnancy outcomes among women with hypertension in pregnancy

Background: Marijuana has vasoconstrictive properties and its use has been associated with increased blood pressure in the general population. Yet, there are limited data on marijuana use and adverse outcomes among women with hypertension in pregnancy, even though these disorders are associated with severe maternal and fetal morbidity and mortality. Since marijuana is currently the most commonly used illicit drug in pregnancy, there is an urgent need to better understand the potential association between marijuana use and hypertension in pregnancy. Objective: To determine the adverse prenatal effects of marijuana use in women with hypertension in pregnancy. Study design: We conducted a retrospective cohort study among individuals with hypertension in pregnancy that delivered ≥23 weeks’ gestation at Oregon Health & Science University (October 2013–September 2018). The primary exposure assessed was marijuana use, identified by chart review of documented patient self-report or positive urine toxicology screen. Individuals were stratified into two groups by marijuana use: use during pregnancy versus never used. Primary outcomes included composite adverse maternal and neonatal outcomes. Secondary outcomes included individual maternal outcomes, rarer neonatal outcomes and severe features of preeclampsia. Differences were analyzed by Fisher’s exact, t-test, and logistic regression. Significance was determined by alpha = 0.05 for primary outcomes and alpha = 0.01 for secondary outcomes. Results: From 11,825 deliveries, 1,613 (13.6%) were classified with hypertension in pregnancy. A total of 117 individuals (7.3%) used marijuana during pregnancy, 1,110 (68.2%) had never used marijuana and 396 (24.6%) had unknown marijuana use and were excluded, leaving 1,217 individuals in this analysis. Women using marijuana in pregnancy were more likely to be younger, non-Hispanic White, publicly insured and using other substances compared to women who did not use marijuana. There were no differences in the overall distribution of hypertensive disorders, including preeclampsia with severe features, in women who used marijuana versus those who did not (p =.80). In multivariable analyses, after adjusting for maternal factors and other substance use, marijuana use was not associated with adverse maternal (aOR 1.23, 95% CI 0.43–3.50, p =.69) or neonatal (aOR 0.90, 95% CI 0.28–2.89, p =.86) outcomes. Conclusions: Marijuana use in pregnancy was not associated with maternal or neonatal outcomes or worsened hypertensive disease among women with hypertension in pregnancy after adjusting for maternal characteristics, including use of other substances. Our data highlight the need to consider use of other substances when evaluating the association between marijuana use in pregnancy and adverse pregnancy outcomes.