Blood flow to the uterus is around 700 mL/minute at term and bleeding can be dramatic and rapidly fatal. Risk factors for obstetric haemorrhage include placenta praevia, placental abruption and postpartum haemorrhage (most commonly due to uterine atony). Obstetric haemorrhage is a major problem in less developed countries, responsible for half of the approximately 500 000 maternal deaths each year across the world. Major haemorrhage remains an important cause of maternal mortality in the UK, with an incidence of 3.7 per 1000 births and nine deaths in 2006–2008. Analysis by the UK Centre for Maternal and Child Enquiries (CMACE) (http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.2010.02847.x/pdf) shows that the management of fatal cases was often suboptimal with underestimation of the degree of haemorrhage and poor team working. The Centre emphasises the need for:
Obstetric haemorrhage is often complicated by disseminated intravascular coagulation (DIC) and defibrination. The primary treatment is evacuation of the uterine contents but supportive therapy with fresh frozen plasma (FFP), cryoprecipitate (or fibrinogen concentrate) and platelet transfusion is often required. There is increasing evidence that the antifibrinolytic agent, tranexamic acid, can significantly reduce mortality in major obstetric haemorrhage and this is being explored in a large international randomised trial (the WOMAN trial – http://www.thewomantrial.lshtm.ac.uk/).
The Royal College of Obstetricians and Gynaecologists has produced guidelines on the prevention and management of postpartum haemorrhage (http://www.rcog.org.uk/womens-health/clinical-guidance/prevention-and-management-postpartum-haemorrhage-green-top-52). Obstetric and anaesthetic staff of appropriate seniority must be involved and access to expert haematological advice is important. Transfusion support for patients with major obstetric haemorrhage should follow the basic principles discussed in Chapter 7. There must be rapid access to compatible red cells and blood components, including emergency group O RhD negative blood. Use of intraoperative cell salvage (ICS) by teams experienced in the technique reduces exposure to donor red cells and can be life-saving, especially in women who decline allogeneic blood transfusion. Use of ICS in obstetrics is endorsed by the National Institute for Health and Care Excellence (NICE). Salvaged blood should be transfused through a leucodepletion filter (see Chapter 6).
The dose of tranexamic acid used in the WOMAN trial is 1g by intravenous injection as soon as possible; a second dose is given if bleeding persists after 30 minutes or recurs within the first 24 hours.