Haemophilia is uncommon in females and little is known about the clinical manifestations and postpartum management of women with this disorder. Clinical characteristics of postpartum bleeding were evaluated in women with factor IX deficiency (FIX:C < 0.20 U mL(-1)), including two with haemophilia B and three carriers of haemophilia B, undergoing labour and delivery. Data were collected prospectively during routine outpatient comprehensive haemophilia care at the haemophilia Center of Western Pennsylvania and during inpatient management. Four of five women experienced postpartum bleeding, during six of 16 deliveries: the median haemoglobin was 10.7 g% and two required blood transfusion. Postpartum bleeding was significantly more common among those receiving fewer than 4 days of FIX replacement: six of 13 (46.1%) receiving fewer three or fewer days bled vs. none of three (0%) receiving six or more days treatment [P < 01 (Wilcoxon)]. Postpartum bleeding was not related to the route of delivery (P = 0.525), vaginal vs. Caesarean, nor the FIX level (P = 0.371; FIX > 0.05 U mL(-1) vs. < or =0.05 U mL(-1)). Compared with females with von Willebrand disease or FXI deficiency, females with FIX deficiency were more likely to experience postpartum bleeding (P = 0.008) and anaemia (P = 0.045); and they were less likely to experience menorrhagia (P = 0.065), but the latter did not reach significance. Postpartum bleeding is common in women with haemophilia B or carriers of haemophilia B, and treatment with factor replacement for at least 4 days of postpartum may prevent bleeding following delivery in such women.