The Liberalization of Cannabis Possession Laws and Birth Outcomes: A State-Level Fixed Effects Analysis, 2003–2019

As states liberalize their cannabis laws, cannabis use has become more widespread among adults across the United States, including pregnant women. As a result, recent research has investigated the potential effects of prenatal cannabis use on child health, with mixed results. In this study, we investigate the relationship between the liberalization of state-level cannabis possession laws and two birth outcomes indicative of child health: birthweight and gestational age. Drawing on 2003–2019 data from CDC WONDER, the American Community Survey, and multiple legal databases, we use fixed effects models to examine how changes in cannabis policies—moving from a misdemeanor to decriminalized to legalized possession—have influenced state-level averages in birthweight and gestational age and percentages of births classified as low birthweight (< 2500 g) and preterm (< 37 weeks). We account for state-level factors including medical cannabis laws, health-related policies, spending patterns, and demographic characteristics known to influence health. Results indicate that the liberalization of state cannabis possession laws was associated with statistically significant reductions in average birthweight, and to a lesser extent gestational age, with significant effects for subgroups of women by age, race/ethnicity, and risk factors including chronic hypertension and diabetes. However, we did not find increases in the percentage of women with clinically relevant low birthweight or preterm births following cannabis policy liberalization. Although our study does not show substantial changes in adverse birth outcomes, policymakers should be attentive to opportunities to strengthen child health by considering policies that minimize consumption, particularly heavier forms of consumption, by prospective parents.