A satisfactory definition of PPH does not exist, but traditionally, primary PPH is defined as a blood loss of 500 mL or more from the genital tract within 24 h from the birth of a baby, and it can be minor (500–1000 mL), moderate (1000–2000 mL), or severe (more than 2000 mL). Massive PPH has been defined as a bleeding >2500 mL and is associated with significant morbidity such as hysterectomy and need for intensive care admission (http://​www.​healthcareimprov​ementscotland.​org). The amount of blood loss is very difficult to clinically assess and is usually underestimated [1]. Other definitions of PPH are the following: a decline in hemoglobin of 4 g/dL or more, transfusion of at least 4 units of red blood cells, or the need for embolization or operative intervention.

A recent systematic review [2] has estimated a global prevalence of PPH to be 10.8 % and severe PPH to be 2.8 %.

It is well known that there is a regional variation of postpartum hemorrhage (≥500 mL) ranging from 7.2 % in Oceania to 25.1 % in Africa, while the prevalence of a blood loss equal or above 1000 mL is higher in Africa (5.1 %) and lower in Asia (1.9 %).

In developed countries such as Europe and North America, the prevalence is around 13 %, being higher for multiple pregnancies (32.4 % compared with 10.6 % for singletons) and for first-time mothers (12.9 % compared with 10.0 % for women in subsequent pregnancies). Furthermore there are some evidences of an increased incidence in PPH in Canada, the UK, Australia, and the USA between 2001 and 2006 related to a rise in obesity.

On the contrary it is possible that the lower prevalence of PPH in Asian women is related to regional differences in genetics or underlying risk factors such as a lower incidence of obesity in Asia.

There are several causes of PPH, classified according to their underlying pathophysiology: tone (uterine atony), tissue (placenta accreta, percreta, increta, previa), trauma (laceration of cervix, vagina), and thrombin (congenital coagulation disorders). Uterine atony is the leading cause of massive obstetric hemorrhage, difficult to be predicted.

To date there are mainly two different strategies to monitor coagulation changes during PPH: the first is based on standard laboratory tests (PT/aPTT and Clauss fibrinogen) and the second on point-of-care coagulation testing devices such as thromboelastometry/thromboelastography.

Despite the hemostatic derangement, standard coagulation tests (PT/aPTT) remain normal until the blood loss reaches 4000–5000 mL, while the fibrinogen levels fall earlier than the other coagulation factors [8]. Recent data show that a low Clauss fibrinogen (<2 g/L) and a reduced maximum amplitude at the ROTEM device are accurate biomarkers for the progression to severe PPH, and the recent ESA guidelines [9] recommend thromboelastometric measurements in order to identify the contribution of fibrinogen to clot strength.

Conventional coagulation tests typically require 45–60 min to be available; they are not adequate to diagnose hyperfibrinolysis, and their results may not influence the initial resuscitation although they are a useful baseline for later management of blood component therapy.

Viscoelastic tests such as rotational thromboelastometry or thromboelastography are dynamic tests which give information on the whole coagulation process from the initiation of clot formation through fibrinolysis. The major advantages of point-of-care testing are that the clinicians can rapidly identify if the bleeding has a coagulopathic or a surgical origin. Furthermore there is good evidence that the ROTEM FIBTEM A5 assay can be used as a surrogate for Clauss fibrinogen during PPH [7, 10, 11].

In a prospective observational study, Houissoud and associates [11] compared 51 women with PPH to a control group and demonstrated that in ROTEM, FIBTEM clotting amplitudes were lower in the PPH group in comparison with the control group. Furthermore a strong correlation between fibrinogen levels and the FIBTEM parameters was present in both groups. The Clauss fibrinogen threshold of 2 g/L corresponded to a FIBTEM A5 of 6 mm and to a FIBTEM A15 of 8 mm with a sensitivity of 100 % both and a specificity of 87 and 84 %, respectively. It is important to consider that thromboelastometry normal ranges at the time of delivery differ from the nonpregnant normal range. Armstrong and associates [12] studied ROTEM parameters from 60 healthy pregnant women presenting for elective cesarean section and 60 matched nonpregnant female controls presenting for elective surgery and demonstrated that pregnant women had significant lower INTEM CT, CFT, and EXTEM CFT (p < 0.001) and higher MCF in INTEM, EXTEM, and FIBTEM (p < 0.001) in comparison to the control nonpregnant group.

De Lange et al. [5] in a Dutch multicenter study reported ROTEM reference values after having collected blood samples from 161 women at two different times: time 1 during labor between 6 and 10 cm cervical dilatation or before elective cesarean section and time 2 within 1 h of delivery of the placenta. They found a shorter CT and CFT in EXTEM and INTEM and larger A10, A20, and MCF in INTEM and FIBTEM in pregnant women in comparison with reference values in nonpregnant adults. Parameters before and after labor were not different, and there was a strong correlation between ROTEM FIBTEM and fibrinogen concentration.

All these data are extremely important because of the increasing use of viscoelastic tests in postpartum hemorrhage management and in order to define specific triggers for hemostatic therapy in this setting.

Rapid diagnosis and early treatment of PPH are critical for a favorable patient outcome. It is well known that the underestimation of the speed and extent of hemorrhage, delay in blood transfusion, lack of treatment algorithm, lack of adequate education and training, poor communication, and deficiencies in organization [13] are responsible for failures in treatment.

The hemostatic management of PPH is challenging, and current guidelines rely on experience from the nonpregnant population and expert opinion.

Three different approaches are used to date for the management of PPH: a laboratory-driven approach, a formula-driven one, and, more recently, a goal-directed strategy based on viscoelastic coagulation monitoring.