More than half of repeat pregnancies with short interpregnancy intervals (≤18 months between live birth and conception of a subsequent pregnancy) are unintended.1 Unintended and short interval pregnancy has significant adverse health and socioeconomic outcomes for women and their families. The immediate health impacts include increased risk of preterm birth, low birth weight, preeclampsia, maternal depression and intimate partner violence, and lower rates of breastfeeding.2-5,20 In the longer-term, unintended childbearing is associated with higher rates of poverty and less family stability.8 Young, poor, black and Hispanic women, and women of lower income or education are more likely to experience unintended short interval pregnancy.6,7 Due to these consequences, a 2030 Healthy People objective is to reduce short interval pregnancies by 20%.9 Receipt of highly effective birth control like long-acting reversible contraception (LARC) in the immediate postpartum period (IPP; time between delivery and hospital discharge) can reduce unintended and short interval pregnancy. Yet, 40-75% of women who plan to use a LARC method postpartum do not receive it.10 A primary barrier to widespread adoption of IPP LARC has been the inability to obtain reimbursement for LARC devices and insertion provided immediately postpartum. To address this barrier, some state Medicaid programs have started to reimburse for IPP LARC insertion, for the device, or both outside of the reimbursement of labor and delivery costs. Absent this policy, states pay for labor and delivery services using a “bundled” payment that does not allow for reimbursement of individual procedures, drugs, or devices. Existing evidence for Medicaid IPP LARC reimbursement is limited to analyses within single hospitals or single states looking at short-term effects of policy adoption (e.g., hospital implementation and LARC uptake) or rely on methods that assume that all factors affecting pregnancy outcomes can be accounted for with covariates. This study seeks to fill gaps in the evidence by examining long-term, population-level effects utilizing a quasi- experimental research design. First, I will estimate the effect of Medicaid IPP LARC reimbursement policy on the probability of using a LARC method postpartum and probability of an unintended pregnancy. Next, I will estimate the effect of the reimbursement policy on the risk of short interval pregnancy. Lastly, I will estimate the extent to which hospital type impacts the risk of short interval pregnancy. Three types of hospitals, teaching hospitals, hospitals with a high proportion of Medicaid patients, and 340B entities, may be more responsive to the policy change because these hospitals serve populations of women at increased risk for short interval pregnancy and have supportive structures to successfully implement a IPP LARC program.12,13 This proposal is aligned with multiple AHRQ research priorities, including racial/ethnic minorities, low-income, ...