Post-partum haemorrhage (PPH) refers to an estimated blood loss in excess of 500 ml following a vaginal birth and a loss greater than 1000 ml during a Caesarean section. Major haemorrhage is defined as an estimated blood loss of more than 2500 ml or the transfusion of 5 or more units of blood or treatment of coagulopathy.
These values are arbitrary as visual estimation of blood loss is not reliable. Patients with a low body mass index have a lower blood volume of 70 ml/kg and anaemic women have fewer reserves to withstand blood loss and hence will decompensate sooner. Thus, a useful definition takes into account any blood loss that causes a major physiological change like a fall in blood pressure, as the risk of dying from PPH depends on the amount and rate of blood loss and the woman’s health.
PPH is classified as primary and secondary. Primary PPH occurs within 24 hours of delivery and secondary PPH after 24 hours and within 6-12 weeks post-partum.
Causes and risk factors
PPH is commonly due to one or a combination of four processes referred to in the ‘4Ts’ mnemonic:
• tone (post-delivery poor uterine contraction)
• tissue (blood clots and/or retained products of conception)
• trauma (genital tract)
• thrombin (coagulation abnormalities).
Common risk factors for PPH are an over-distended uterus due to fetal macrosomia, multiple pregnancy and polyhydramnios. Antepartum haemorrhage, chorio-amnionitis, coagulation disorders, fibroid uterus, induction of labour, instrumental delivery, obesity, pre-eclampsia, previous Caesarean section delivery, previous history of PPH, primigravidity, prolonged rupture of membranes and/or labour are also considered to be risk factors.
There is a trend in the UK towards delaying child-bearing. Increased maternal age, Caesarean and instrumental deliveries and placenta praevia increase the incidence of PPH. An increasing number of multiple pregnancies due to assisted reproduction can also result in an increased incidence of PPH.
PPH can occur in women without identifiable risk factors. In absolute numbers, more women without risk factors have atonic PPH as compared with those with risk factors.
Pathophysiology
The blood vessels supplying the placental bed pass through an interlacing network of muscle fibres of the myometrium. Myometrial contraction causes placental separation and causes blood vessels to constrict. This haemostatic mechanism or ‘living ligatures’ control the bleeding from the placental bed when the placenta separates. Uterine atony results in a failure of these ‘living ligatures’ to stop the bleeding. The active management of the third stage of labour is associated with a reduction in the risk of PPH and less need for blood transfusion by enhancing the above physiological process.
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Mild shock occurs when 20% of the blood volume is lost, resulting in decreased perfusion of non-vital organs and tissues (i.e. bone, fat, skeletal muscle) with pale and cool skin. When 20-40% of the blood volume is lost, moderate shock occurs with decreased perfusion of vital organs (i.e. gut, kidneys, liver), oliguria and/or anuria, a drop in blood pressure, and mottling of the skin in the legs. When 40% or more of the blood volume is lost, severe shock occurs resulting in decreased perfusion of the heart and brain, agitation, restlessness, coma, echocardiogram and electroencephalogram abnormalities, and finally cardiac arrest.
Prevention of PPH
Only 40% of women who develop PPH have an identifiable risk factor. Women with risk factors should be delivered in centres with transfusion and intensive care unit facilities. The Royal College of Obstetricians and Gynaecologists (RCOG) urges early or prophylactic interventional radiology for the prevention and management of PPH in high-risk cases and recommends strategies for the management of unpredicted PPH.
Prevention of PPH includes antenatal risk assessment and treatment of anaemia or other health problems so that women are healthy enough to withstand PPH, as well as appropriate intra-partum and post-partum management. The International Confederation of Midwives and the International Federation of Gynecology and Obstetrics (FIGO) have together launched a world-wide programme to promote active management of the third stage of labour for all women. Active management consists of interventions designed to facilitate placental delivery by improving uterine contractions and preventing PPH by averting uterine atony. These measures include administration of uterotonic agents, controlled cord traction and uterine massage after delivery of the placenta, as deemed appropriate. This approach reduces the risks of PPH, anaemia, requirement for blood transfusion, prolonged third stage of labour and use of therapeutic drugs for PPH. It is recommended that active management should be routine for women in maternity hospitals and there is no evidence to suggest that this recommendation should not include low-risk births at home or in birth centres.
Oxytocin is used routinely in the active management of the third stage of labour. It is routinely administered for the prevention and treatment of PPH as a first-line agent as it is effective within 2-3 minutes after injection and, as it has minimal side effects, it can be used in all women. If oxytocin is unavailable, ergometrine maleate 0.5 mg intramuscularly, ergometrine with oxytocin 5 IU/ml (syntometrine) or misoprostol 0.4 mg orally can be used.
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Misoprostol – which is a prostaglandin E1 analogue – can be administered by oral, sublingual and rectal routes. The main side effects are diarrhoea, nausea and vomiting. Rectal misoprostol causes less shivering and pyrexia, than oral misoprostol. A recent Cochrane review on the use of prostaglandins for the prevention of PPH concluded that neither intramuscular prostaglandins nor misoprostol are preferred to conventional injectable uterotonics as part of the management of the third stage of labour especially for low-risk women.
Carbetocin is a long-acting oxytocin agonist and has been used for the prevention of PPH. The advantage of intramuscular carbetocin over intramuscular oxytocin is its longer duration of action. It induces a prolonged uterine response post-partum, both in amplitude and frequency of contraction. Carbetocin is associated with reduced need for other uterotonic agents and uterine massage, and there are no differences in side effects between carbetocin and oxytocin.
FIGO recommends that skilled birth attendants should use physiological (or expectant) management of the third stage if oxytocin or misoprostol are unavailable.
In 2006, the World Health Organization held a technical consultation on the prevention of post-partum haemorrhage and it recommends the following.
• Active management of the third stage of labour should include: administration of an uterotonic soon after the birth of the baby; delayed cord clamping; and delivery of the placenta by controlled cord traction followed by uterine massage.
• Active management of the third stage of labour should be offered by skilled attendants, as potential risks such as uterine inversion, may result from inappropriate cord traction.
• Oxytocin should be offered for the prevention of PPH in preference to oral, sublingual or rectal misoprostol.
• In the absence of active management of the third stage of labour, an uterotonic drug (oxytocin or misoprostol) should be offered.
Conclusions
PPH is a major cause of maternal morbidity and mortality. Identification of risk factors antenatally and intra-partum is useful in the prevention and treatment of PPH. Catastrophic and life-threatening haemorrhage is often unpredictable. Prompt resuscitation of the patient with effective restoration of the circulating blood volume and identification of the cause of bleeding should be performed in a multidisciplinary team setting. Rapid and prompt treatment measures should be instituted in a step-wise manner using the algorithm ‘HAEMOSTASIS’ and assessment tools such as the ‘rule of 30’ and the ‘shock index’. Protocols for the prevention and management of PPH should be constantly updated in every maternity unit. The training of all members of staff in the management of this common obstetric emergency should include regular ‘fire drills’.
• Specific management of controlling PPH should go hand in hand with fluid, blood and clotting factor resuscitation
• Every unit should have a protocol to manage PPH in a stepwise manner
• Medical management should precede surgical management
• Simple surgical management (tamponade, brace sutures) is less time-consuming, can be done with minimal training and is effective in more than 80% of cases
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