Assessing the Risks of Postpartum Haemorrhage


Published: 20 May 2018

Somewhere in the world a woman dies every 4 minutes from postpartum haemorrhage (Durdas 2012).

As well as being a terrifying experience for the mother it can also be one of the most serious and alarming emergencies that a Midwife has to manage. So, can the risks of postpartum haemorrhage occurring be accurately assessed?

The Challenge of Accurate Assessment

Postpartum haemorrhage (PPH) is generally defined as blood loss of more than 500 ml following vaginal delivery or more than 1000 ml following caesarean delivery. However, as Smith (2017) suggests the definition of PPH is actually somewhat arbitrary and problematic.

Estimates of blood loss at delivery can be subjective and often inaccurate with a tendency for caregivers to underestimate blood loss. Large volumes of blood can soak into bed linen and solidified clots may only represent about half of the actual blood that has been lost.

Smith (2017) suggests that another consideration in assessing the risks of PPH is the differing capacities of individual women to cope with blood loss. A healthy woman has a 30-50% increase in blood volume in a normal singleton pregnancy and is much more tolerant of blood loss than a woman who has pre-existing anaemia, an underlying cardiac condition, or a condition secondary to dehydration or preeclampsia.

Women with a low body mass index also have a lower blood volume, tend to have fewer reserves to withstand significant blood loss and so are likely to experience adverse physiological effects sooner. For these reasons, it’s suggested that PPH should be diagnosed when any amount of blood loss, however small, threatens the hemodynamic stability of the woman.

Grading the Severity of Blood Loss

Although accurately assessing the volume of blood loss can be difficult, the following classifications are generally used to grade the extent of the haemorrhage.

Minor Primary Postpartum Haemorrhage

  • The loss of 500-1000mls of blood from the genital tract within 24 hours of the birth of a baby.

Major Primary Postpartum Haemorrhage

  • The loss of over 1000mls of blood from the genital tract within 24 hours of the birth of a baby.

Massive Primary Postpartum Haemorrhage

  • Blood loss >2000ml or rate of blood loss of 150ml/min, or 50% blood volume loss within 3hrs.

Secondary Postpartum Haemorrhage

  • Abnormal or excessive bleeding from the birth canal between 24 hours and up to 12 weeks post-delivery.

(Royal Cornwall Hospitals NHS Trust 2018)

Two doctors holding a baby sitting up after birth | Image

The 4 ‘T’s of Postpartum Haemorrhage

Postpartum haemorrhage is usually considered to be caused by one or more of the four processes referred to in the ‘4Ts’ mnemonic:


  • Failure of the myometrium to contract adequately (atonic uterus) after the birth is generally regarded as the most common cause of PPH.


  • Blood clots and retained products of conception. The placenta and membranes should be checked to ensure they are complete.


  • A vaginal examination should be carried out to check for any bleeding from the genital tract.

Thrombin (abnormalities of coagulation)

  • The woman’s blood loss should be observed to assess whether it is clotting.

(Royal College of Midwives 2014)

Common Risk Factors for Postpartum Haemorrhage

Some women are at greater risk of postpartum haemorrhage than others. Conditions that are generally recognised to increase the risks of PPH include:

  • Overdistended uterus. Excessive enlargement of the uterus due to polyhydramnios or a large baby, especially with a birthweight over 4,000 grams.
  • Placental abruption. The early detachment of the placenta from the uterus.
  • Placenta previa. The placenta covers or is near the cervical opening.
  • Multiple pregnancy. More than one placenta and overdistention of the uterus.
  • Gestational hypertension
  • Having many previous births
  • Prolonged labour
  • Infection
  • Obesity
  • Medications to induce labour
  • Instrumental delivery
  • General anaesthesia
  • Tear in the cervix or vaginal tissues
  • Tear in a uterine blood vessel
  • Bleeding into a concealed tissue area or space in the pelvis which develops into a hematoma, usually in the vulva or vaginal area
  • Blood clotting disorders, such as disseminated intravascular coagulation

(Stanford Children’s Health 2018)

In addition to these general factors, Nyfløt (2016) also suggests that assisted reproductive technology (ART) could also be associated with an increased risk of severe PPH, particularly amongst women with multiple pregnancies.

Results of recent research suggest that women with the combination of an ART pregnancy and multiples were considerably more at risk of severe PPH (4.5 %) than among the women in the control group (0.3 %).

All women who carry a pregnancy beyond 20 weeks’ gestation are at risk of PPH (Smith 2017) and although maternal mortality rates have declined significantly in the developed world, PPH still remains a leading cause of maternal mortality elsewhere.

As Souza (2013) reports significant haemorrhage post delivery remains associated with one-quarter of all maternal deaths and severe maternal morbidities throughout the world.

Clinical Signs and Symptoms of Postpartum Haemorrhage

One of the challenges when assessing the extent of postpartum haemorrhage is that the clinical signs of haemorrhagic shock can be masked in a newly delivered woman due to the increased blood volume of pregnancy.

In most cases however, postpartum haemorrhage is accompanied by one or more of the following clinical signs and symptoms depending on the amount of blood lost:

  • Palpitations
  • Dizziness
  • Tachycardia
  • Weakness
  • Sweating
  • Restlessness and pallor
  • Potential ultimate collapse.

(Royal College of Midwives 2014)

According to D’alton (2017), postpartum haemorrhage remains a significant cause of maternal mortality with primary PPH occurring between 1% and 5% of all deliveries, and secondary PPH occurring between 0.2% and 2% of all pregnancies.

Based on data collected by the Royal College of Midwives the incidence of major obstetric haemorrhage is 3.7 per 1000 births and is still recognised as one of the leading causes of maternal death (RCM 2012), with no significant reductions in the UK death rate since 2009 (Merrifield 2016).

However, collecting accurate data on PPH is difficult and in the view of Flood et al. (2018), reporting on a national Australian rate is not possible due to lack of nationally consistent definitions and details.

Can Anything be Done to Lower the Risk of PPH?

Severe bleeding remains the primary cause of maternal death worldwide, yet in the view of Durdas (2012) up to 75% of those deaths may be preventable.

However, in less well developed countries it could be argued that the risk factors of excessive bleeding may be harder to anticipate, or prevent.

Likewise, in developed countries, the trends towards increased maternal age, higher rates of instrumental deliveries and use of assisted reproductive technologies also results in an increased incidence of PPH.

These factors taken together make it difficult, if not impossible to significantly lower the risks of PPH, leaving it a major contributor to maternal mortality.

Whilst identification of risk factors antenatally and intra-partum can be useful in the management of PPH, life-threatening haemorrhage is often unpredictable.

Even with the highest standards of care, 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 that are clearly identified (Durdas 2012).

With death rates remaining unacceptably high the key focus of maternity protocols has to remain on the recognition of risk factors, rather than expectations of lowering them.

Ultimately it is only with anticipation, comprehensive policies on the management of obstetric emergencies and prompt mobilisation of resources that lives can be saved.