A retrospective review was performed over a period of 5years (July, 1972, to July, 1977) from the delivery records at Women's Hospital of the Los Angeles County/University of Southern California Medical Center. During this time period, there were 60,052 deliveries and 28 cases of puerperal uterine inversion for an incidence of 1 in 2,148. The mean age of the primiparous patients was 19.1years (N=15) and that of the multiparous patients was 23.2years (N=13). The mean blood loss was greatest in primiparous patients, although blood loss was significant in each group. All patients were delivered by house officers in their first postgraduate year of training or by students under supervision. There was no significant difference between the lengths of the first and third stages of labor in either the primigravid or multigravid patient groups. The length of the second stage of labor was decreased in the multiparous patients compared to the primigravid group. Shock was clinically diagnosed in only 8 of 28 cases (28.5%). It was noted that 9 of 28 patients (32%) had received parenteral magnesium sulfate as therapy for the diagnosis of preeclampsia. In addition, six of these nine patients were receiving concomitant oxytocin infusion for augmentation of labor. There were three other patients receiving oxytocin infusion only. Prophylactic antibiotics were used in 11 patients and febrile morbidity occurred in two patients (18%). There were four cases (23%) of puerperal infectious morbidity among the 17 patients who did not receive antibiotics. The difference between these groups is not significant. These data would suggest: (1) that parenteral magnesium sulfate administration with or without concomitant oxytocin infusion may be an additional predisposing cause of acute puerperal uterine inversion and (2) that treatment with prophylactic antibiotics offers no additional benefit.