INTRODUCTION: Improvement of care during the 90 days postpartum (“4th trimester”) is needed. Fifty percent of women return for their postpartum office visit; 10% use the emergency department (ED). We evaluated what factors might be associated with postpartum ED usage METHODS: This retrospective cohort study from an urban hospital-based clinic compared women who visited the ED within 90 days postpartum (Group 1) to women who did not visit the ED (Group 2). Variables assessed: age, marital status, race, delivery gestational age, parity, ED visits during the year prior to conception. We performed regression analysis to determine independent variables associated with ED usage 90 days postpartum. A P<.05 was significant. IRB approval was obtained for this study. RESULTS: Of 1297 women, there were 190 (14.8%) in Group 1. This group visited the ED 252 times (48.0% for non-emergent diagnoses). Three variables were significant. Group 1 women with cesareans (OR 1.77, 95% CI 1.29-2.42), women who visited the ED in the year prior to conception (OR 2.00, 95% CI 1.45-2.75) and frequent (≥3 visits/year) ED users (OR 2.94, 95% CI 1.84-4.62) were more likely to visit the ED in the 4th trimester versus Group 2. CONCLUSION: We found that women who visit the ED and were frequent users prior to pregnancy are more likely to continue that usage during the postpartum. Understanding risk factors for maternal ED usage is important as initiatives and care plans are developed during pregnancy for preemptive education and postpartum care.