Severe postpartum haemorrhage (PPH) is defined as blood loss ≥1000 mL within the first 24 h of delivery [1]. A systematic review of the literature including 123 databases between 1994 and 2008 estimates an incidence of 2.8 % for severe PPH [2], making it the most frequent complication of childbirth. Uterine atony represents the main cause of PPH, responsible for 50 to 80 % of PPH regardless of the type of delivery [3]. The incidence of maternal mortality due to PPH is decreasing in France, but it still remains the second cause of maternal mortality (one death per 100,000 live births) according to the latest confidential national survey conducted from 2013 to 2015 [4]. According to this report, 88.9 % of these deaths are still considered to be avoidable.

Transfusion strategy is an essential element in the management of PPH. According to French national recommendations, the main purpose of red blood cell (RBC) transfusions is to maintain a hemoglobin (Hb) level above 8 g/dL in the event of active bleeding [1]. However, defining the criteria necessary to initiate RBC transfusion is difficult to realize, as many variable factors must be taken into consideration such as hemoglobin levels, the cause of PPH and the flowrate of bleeding, maternal clinical tolerance and management conditions. A threshold of Hb around 7.0 g/dL is generally accepted in subjects with no previous cardiovascular history (professional agreement) [5]. The American College of Obstetricians and Gynecologists recommends: "in women with ongoing bleeding that equates to the blood loss of 1500 mL or more or in women with abnormal vital signs (tachycardia and hypotension), immediate preparation for transfusion should be made" [6]. The International Federation of Gynecology and Obstetrics does not propose any hemoglobin objectives nor thresholds in their recommendations for hemostatic resuscitation [7]. In the same way the Royal College of Obstetricians and Gynaecologists (RCOG) writes: "there are no firm criteria for initiating red cell transfusion. The decision to provide blood transfusion should be based on both clinical and haematological assessment" [8]. However, the RCOG summarizes the guidance from the British Committee for Standards in Haematology and the main therapeutic goals of the management of massive blood loss as maintaining Hb greater than 8.0 g/dL, prothrombin time (PT) less than 1.5 times normal, activated partial thromboplastin time (APTT) less than 1.5 times and fibrinogen greater than 2.0 g/L.

Risk factors associated with severe maternal morbidity [9] or massive perinatal blood transfusion [10,11], prediction models for RBC transfusion [12] in severe PPH context have already been described in large population-based cohort studies. In this study, we wanted to focus on factors and events occurring during the management of severe PPH.

The primary purpose was to identify the main clinical and biological factors, which are available during the management by the clinicians (obstetricians and anesthesists) and significantly associated with RBC transfusion decision in the first 24 h of severe PPH. The secondary objectives were to describe the obstetrical, surgical and transfusion management of severe PPH and to assess the concordance of the transfusion management with the french national recommendations.