Maternal and newborn health in the United States continues to face disparities in access, quality, and affordability. This dissertation examined whether state policies, Medicaid financing, and market regulation influence care and outcomes. Study 1 analyzed National Vital Statistics System birth records (2009–2023) to assess other-attended births, an indirect indicator of non-physician, non-midwife attendance. Medicaid doula reimbursement showed no association with changes in this measure, and evidence of variation by pre-policy context was limited. Study 2 used hospital discharge data from New Jersey (2019–2022). The policy was associated with reductions of 1.05 percentage points in cesarean deliveries and 0.51 percentage points in preeclampsia among Medicaid-covered births compared with private insurance; county differences were not statistically significant. Study 3 examined state hospitalization data (2008–2022). Recreational cannabis legalization did not show a significant average change in neonatal abstinence syndrome hospitalization rates; however, suggestive reductions were seen in states with younger maternal ages. Across all studies, policy adoption did not consistently lead to uniform population-level changes. These findings underscore the importance of distinguishing between policy authorization and implementation, considering individual exposure, allowing policies time to be operational, and aligning evaluation measures with the pathways through which policies impact health.