ImportancePostpartum emergency department (ED) visits may indicate poor access to care and risk for maternal morbidity.ObjectivesTo identify patient and hospital characteristics associated with postpartum ED visit rates.Design, Setting, and ParticipantsThis retrospective cohort study used data from the 2014 to 2016 New York State Inpatient Database and State Emergency Department Database. All obstetric discharges from acute care hospitals in New York State from January 1, 2014, through November 15, 2016, were included. Obstetric discharges in the inpatient database were linked to subsequent ED visits by the same patient in the ED database. Data were analyzed from February 2020 to August 2022.ExposuresPatient characteristics assessed included age, race, insurance, home zip code income quartile, Charlson Comorbidity Index score, and obstetric risk factors. Hospital characteristics assessed included safety net status, teaching status, and status as a hospital disproportionally serving racial and ethnic minority populations.Main Outcomes and MeasuresThe primary outcome was any ED visit within 42 days of obstetric discharge. Multilevel logistic regression with 2-level nested mixed effects was used to account for patient and hospital characteristics and hospital-level clustering.ResultsOf 608 559 obstetric discharges, 35 299 (5.8%) were associated with an ED visit within 42 days. The median (IQR) birth hospital postpartum ED visit rate was 6.3% (4.6%-8.7%). The mean (SD) age was 28.4 (9.1) years, 53 006 (8.7%) were Asian patients, 90 675 (14.9%) were Black patients, 101 812 (16.7%) were Hispanic patients, and 275 860 (45.3%) were White patients; 292 991 (48%) were insured by Medicaid, and 290 526 (47.7%) had private insurance. Asian patients had the lowest postpartum ED visit rates (2118 ED visits after 53 006 births by Asian patients [3.99%]), and Black patients had the highest postpartum ED visit rates (8306 ED visits after 90 675 births by Black patients [9.15%]). Odds of postpartum ED visits were greater for Black patients (odds ratio [OR], 1.31; 95% CI, 1.26-1.35; P < .001) and Hispanic patients (OR, 1.19; 95% CI, 1.15-1.24; P < .001) relative to White patients; those with Medicare (OR, 1.55; 95% CI, 1.39-1.72; P < .001), Medicaid (OR, 1.37; 95% CI, 1.34-1.41; P < .001), or self-pay insurance (OR, 1.50; 95% CI, 1.41-1.59; P < .001) relative to commercial insurance; births that occurred at safety net hospitals (OR, 1.43; 95% CI, 1.37-1.51; P < .001) and hospitals disproportionately serving racial and ethnic minority populations (OR, 1.14; 95% CI, 1.08-1.20; P < .001); and births that occurred at hospitals with fewer than 500 births per year (OR, 1.25; 95% CI, 1.14-1.39; P < .001) relative to those with more than 2000 annual births. Adjusted odds of postpartum ED visits were lower after birth at teaching hospitals (OR, 0.82; 95% CI, 0.74-0.91; P < .001) and metropolitan hospitals (OR, 0.74; 95% CI, 0.65-0.85; P < .001).Conclusions and RelevanceThis cohort study found that Black and Hispanic patients experienced higher adjusted odds of postpartum ED visits across all hospital types, particularly at safety net hospitals and those disproportionately serving racial and ethnic minority populations . These findings support the urgent need to mitigate structural racism underlying maternal health disparities.