Some 358,000 women die each year in childbirth, mostly in developing countries (WHO 2010). Severe bleeding in the postpartum period is the single most important cause of maternal deaths worldwide (AbouZahr 2003; Khan 2006). More than half of all maternal deaths occur within 24 hours of giving birth, most commonly from excessive blood loss. Depending on the rate of blood loss and other factors such as pre-existing anaemia, untreated postpartum haemorrhage (PPH) can lead to hypovolaemic shock, multi-organ dysfunction and maternal death within two to six hours. As it is stated in the most recent edition of Confidential Enquiries into Maternal Deaths in the United Kingdom (Lewis 2011), during 2006 to 2008 there were nine direct maternal deaths from obstetric haemorrhage, including one associated with a uterine rupture. These nine direct deaths from obstetric haemorrhage represent a decline from the 14 that occurred during 2003 to 2005, where a rate of 0.66 per 100,000 maternities (95% confidence interval 0.39 to 1.12) was reported (P = 0.2). Consequently, this triennium, obstetric haemorrhage is reduced to being the sixth leading cause of direct maternal deaths and the mortality rate is the lowest since the UK-wide Confidential Enquiry Reports began in 1985 (Lewis 2011).
Description of the condition
The third stage of labour refers to the period between the birth of the baby and complete expulsion of the placenta and membranes. Blood loss during this period and immediately thereafter depends on how well the placenta separates from the uterine wall and how well the uterus contracts to close the vascular channels in the placenta bed. Other causes of PPH include vaginal or cervical tears, uterine rupture, retained placenta or membranes, abnormal adherence of the placenta or altered homeostasis. Moderate loss of blood is physiological and unlikely to lead to later problems except for women who are already anaemic. The major complication associated with this stage is PPH. This is not necessarily excessive bleeding, and according to the World Health Organization (WHO), PPH is defined as bleeding from the genital tract in excess of 500 mL after the delivery of the baby (WHO 2000). Alternative cut-off points of 600 mL (Beischer 1986) and 1000 mL (Burchell 1980) have also been suggested. This difference in criteria may be due to the classification of blood loss, as blood loss between 500 mL to 1000 mL is considered moderate and over 1000 mL is defined as severe. Globally, this complication occurs in approximately 6% of all deliveries although the prevalence is disproportionately higher in low-income countries (Carroli 2008). However, variations in the estimated incidence of PPH between 5% and 18% have been reported (Gilbert 1987; Hall 1985), even within a single country like the UK, where PPH remains an important cause of maternal mortality (DoH 2004; Gilbert 1987; Hall 1985).
Nearly all maternal deaths (99%) occur in the developing world (Kwast 1991), where other factors, such as infection (especially HIV infection), poor nutritional status and lack of easy access to treatment, may contribute to death in the presence of severe PPH. Many more women survive and suffer serious illness as a result, not only from the effects of acute anaemia (including Sheehan’s syndrome (a postpartum condition where there is decreased functioning of the pituitary gland resulting from uterine haemorrhage during and after childbirth)), but also from the interventions which a severe haemorrhage may necessitate (such as general anaesthesia, manual removal of the placenta, blood transfusion, hysterectomy). Delay in the diagnosis and treatment of PPH may result from an underestimation of blood loss at delivery, among other causes such as lack of resources or clinical skills to resolve the problem. Assessment of postpartum blood loss, particularly after vaginal birth, is recognised as difficult. Many studies found that visual estimates of peripartum blood loss are often inaccurate (Bose 2006; Didly 2004; Duthie 1991; Newton 2000; Prasertcharoensuk 2000; Razvi 1996; Stafford 2008), showing an overestimation of blood loss of low volumes and an underestimation of larger volumes, the magnitude of underestimation typically increasing with the volume of haemorrhage (Zhang 2010).
Description of the intervention
The current worldwide standard practice of postpartum blood loss assessment is visual estimation of blood loss (VEBL). A healthcare provider generally observes the amount of blood lost during delivery and makes a quantitative or semi-quantitative estimate. Methods to quantitatively estimate postpartum vaginal blood loss include, direct collection and measurement or weighing, venous blood sampling, dye dilution techniques for plasma volume measurement, and red blood cell and plasma volume determinations using radioactive tracer elements. The most accurate measures include venous blood sampling for determination of haemoglobin (Hb) concentration, with and without assessment of blood volume by red blood cell labelling or spectrometry. However, these methods have not been widely adopted because they are neither practical nor affordable in most clinical settings (Patel 2006).
A compensated shock occurs with a blood loss of less than 1000 mL and no change or slight change in clinical signs. Substantial changes in heart rate and blood pressure would be seen after a blood loss of more than 1000 mL. Hypotension with significant tachycardia and a rise in respiratory rates would occur after a loss of 25% to 35% of blood volume and profound shock occurs after a 40% blood loss. However, the use of clinical signs may lack accuracy in the assessment of hypotension and needs further testing in order to help guide the management of PPH. In a recently published systematic review of the relationship between blood loss and clinical signs, the shock index was found to be an accurate indicator of compensatory changes in the cardiovascular system due to blood loss (Pacagnella 2013). The shock index is calculated as the heart rate divided by the systolic blood pressure and this simple calculation may transform unstable parameters into a more accurate predictor of hypovolaemia. In addition, the shock index has been recently suggested as a tool to predict mortality due to hypovolaemic shock in trauma patients. The use of the shock index in the early identification and assessment of bleeding is considered promising even in obstetric populations. Considering that most of the evidence included in the systematic review by Pacagnella et al is derived from studies in non-obstetric populations, further studies on the use of the shock index in obstetric populations are needed.
How the intervention might work
We are evaluating alternative methods for blood loss estimation compared with visual estimation, not in terms of their diagnostic accuracy but for their effectiveness in reducing the adverse consequences of both mild and severe PPH. An effective method should not underestimate the amount of blood loss, hence the appropriate therapeutic measures are not applied timely, and also not overestimate it, leading to unnecessary and potentially aggressive or invasive treatments.
Potential adverse effects
We will assess the potential side effects of those invasive methods that include blood extraction for any measurement or the injection of any substance to be measured for the quantification of blood loss.
Why it is important to do this review
The consequences of severe PPH are widely known. So too is the importance of finding the most accurate method to quantify blood loss during the third stage of labour in order to prevent or, once commenced, to control PPH. Precision is not the only quality the method should have; it also has to be practical and accessible for all, including minimally trained, healthcare providers.