Association between state-level medical marijuana legalization and marijuana use during pregnancy: A population-based study

Background and Objectives: Despite marijuana's association with adverse pregnancy and birth outcomes, its use during pregnancy increased over the last two decades. During this period, medical marijuana has been legalized in 38 states and the District of Columbia. States with legalized medical marijuana have observed increased marketing of marijuana and related products. This study aims to examine the association between state-level medical marijuana legalization and marijuana use during pregnancy in the United States. Methods: Using the 2015–2021 National Survey on Drug Use and Health, we evaluated the association between marijuana use in the past month among currently pregnant mothers (N = 4338) and legalized medical marijuana in their state of residence. Survey-weighted descriptive, bivariate, and multivariable logistic regression analyzes were performed. Results: About 5.7% of pregnant women reported using marijuana in the past month, and 59.0% lived in a state where medical marijuana was legalized across 2015–2021. Compared to those living in states without marijuana legalization, more pregnant women living in states with marijuana legalization reported using marijuana (4.6% vs. 6.5%). In the multivariable model, pregnant women residing in states with medical marijuana legalization were more likely to use marijuana than residents of states without legalization (adjusted Odds Ratio: 1.56; 95% Confidence Interval: 1.11–2.18). Conclusion and Scientific Significance: This is the first known study to find that pregnant women living in states where medical marijuana is legalized are more likely to use marijuana during pregnancy. Pregnant women should be informed of adverse pregnancy and birth outcomes linked to marijuana use during pregnancy.