The Affordable Care Act (ACA) Medicaid expansions increased preconception and postpartum insurance coverage among low-income birthing people, leading to greater use of outpatient care. In this study we evaluated whether the expansions affected rates of postpartum hospitalization. Our analyses took advantage of underused longitudinal hospital data from the period 2010-17 to examine hospitalizations after childbirth. We compared changes in hospitalizations among birthing people with a Medicaid-financed delivery in states that did and did not expand Medicaid under the ACA. We found a 17 percent reduction in hospitalizations during the first sixty days postpartum associated with the Medicaid expansions and some evidence of a smaller decrease in hospitalizations between sixty-one days and six months postpartum. Our findings indicate that expanding Medicaid coverage led to improved postpartum health for low-income birthing people.