The association between the legalization of recreational marijuana and both small for gestational age births and NICU admissions in Colorado.

OBJECTIVE: To determine the association between recreational marijuana legalization and both small for gestational age (SGA) births and neonatal ICU (NICU) admissions in Colorado.

STUDY DESIGN: Using interrupted time series analysis, we compared the incidence of SGA births and NICU admissions pre-/post-recreational marijuana legalization. Secondary analysis adjusted for marijuana outlet density (MOD) in maternal county of residence.

RESULTS: We analyzed 269,922 mother-infant dyads. SGA birth risk dropped 7% immediately post-legalization (p = 0.04), but there was no slope difference between cohorts. SGA birth risk for high MOD dyads was 1.4x that of dyads with no outlets (p < 0.001) and 1.2x that of low MOD dyads (p = 0.002). There was no immediate effect on NICU admission risk, but the slope increased 1%/month post-legalization (p < 0.001) including a 1%/month increase for low MOD and 3%/month for high MOD dyads.

CONCLUSIONS: Incidence of SGA births in Colorado did not change following recreational marijuana legalization. NICU admissions increased post-legalization.