OBJECTIVES: Administration of weekly 17-alpha-hydroxyprogesterone caproate (17P) injections in high-risk pregnancy from 16–24 weeks until delivery reduces pre-term birth (PTB) rates by up to 30%. This retrospective cohort analysis investigated the impact of 17P on gestational age and neonatal intensive care unit (NICU) utilization in 17P-treated versus untreated cohorts. METHODS: The study cohort consisted of Medicaid members (ages 16–45 years) from six geographically diverse managed care organizations with ≥1 estimated gestational live birth registered in our claims database who were administered 17P from 2014–2015 (N=382). The comparator cohort consisted of members with the same high-risk characteristics in the Medicaid population who were not administered 17P, delivering babies from 2013–2015 (N=7,918). Intra-cohort comparisons (pre- versus post-gestational weeks within cohorts) and inter-cohort comparisons (difference-in-differences [DID] estimation between cohorts) for primary outcome measures were calculated using two tailed t-tests and unadjusted generalized least square regression models, respectively. RESULTS: