Background. To examine risk factors and interventions associated with major primary postpartum hemorrhage (PPH) unresponsive to first-line conventional therapy. Methods. From computerized maternity database, we identified women with major primary PPH defined as blood loss ≥1,000 ml and/or the need for a blood transfusion within 24 h of delivery beyond 24 weeks' gestation. Cases were assigned according to the mode of delivery and response to the first-line therapy (responders and non-responders). Results. Between 1998 and 2002, 20,610 women delivered after 24 weeks' gestation. A total of 306 women developed primary PPH (14.8/1,000 deliveries) including 103 vaginal and 203 caesarean (CS) births. Out of 103 women with PPH following vaginal birth, 22 (21%) failed to respond to first-line therapy. Following CS, 20 of 203 (10%) failed first line treatment and required examination under anesthesia (EUA) and other interventions to control bleeding. Irrespective of the mode of delivery, antepartum risk factors did not differ between responders and non-responders to first-line therapy. In the vaginal group, non-responders were treated with required bimanual compression and intra-myometrial PGF₂ (49%), repair of cervical tear (14%), vaginal packing (9%), and uterine packing (5%). In the CS group, hysterectomy was the most common surgical intervention (54%) after other methods including uterine packing, B-Lynch procedure, uterine tamponade, and intra-myometrial prostaglandin were ineffective. Conclusions. The currently known risk factors for primary PPH are not useful in the identification of patients who continue to bleed after first-line therapy. Emergency hysterectomy was the most common surgical intervention used to control major PPH unresponsive to conventional therapy following CS birth.