Objective: To elicit factors associated with the postpartum development of septic pelvic thrombophlebitis in a single large referral tertiary patient population. Methods: A nine-year single institution retrospective case review of all patients with enigmatic fever and septic pelvic thrombophlebitis was analyzed. Results: A total of 55 patients with septic pelvic thrombophlebitis were provided care during the study interval. The average gestational age at delivery was 36.8 +/- 4.3 weeks. The most prevalent concurrent medical complication of pregnancy was preeclampsia (45%) while chorioamnionitis affected only 13%. The average length of ruptured membranes was 22.8 +/- 56.8 hours (median 10.5, 95% confidence interval [CI] 7.0-38.7 hours), with 22% of patients undergoing amnion rupture at the time of cesarean delivery. Prolonged ( > 24 hours) amnion rupture occurred in only 9% of patients. Most affected patients were delivered abdominally (91%) but a minority delivered vaginally (9%). Antibiotic therapy for presumed infection was initiated at 27.4 +/- 24.6 hours postpartum. Subsequently intravenous heparin therapy was initiated 128.9 +/- 54.2 hours thereafter enigmatic fever defervesed 37.2 +/- 36.8 hours later (median 34.0, 95% CI 27.2-47.3 hours). Patients received 6.3 +/- 1.8 days of heparin therapy. Conclusion: In this series, septic pelvic thrombophlebitis was frequently preceded by cesarean delivery and commonly associated with preeclampsia. Unexpectedly, a small number of patients suffered prolonged rupture of membranes or chorioamnionitis. We speculate that the cesarean delivery of a population of at-risk patients with preeclampsia may predispose them to develop septic pelvic thrombophlebitis.