Definition

Primary postpartum hemorrhage (PPH) has been defined as the loss of 500 mL or more of blood within 24 hours of delivery. PPH can be minor (500 to 1000 mL) or major (>1000 mL). Major can be further divided into moderate (1000 to 2000 mL) or severe (>2000 mL).

Most of the cases that cause morbidity or mortality or that present challenges in management have a blood loss greater than 1000 mL.

Although primary PPH is the most common form of obstetric hemorrhage, secondary PPH should not be forgotten. This is defined as abnormal or excessive bleeding from the birth canal between 24 hours and 12 weeks postnatally.

Recognition

PPH occurs in as many as 10% of deliveries. Blood loss may be obvious, such as per vaginum or loss from the surgical wound. However, it can also be concealed and contained within the uterus, soft tissues, or peritoneum. The patient may exhibit the following:

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  Anxiety, confusion, or unresponsiveness

  
  
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  Hypotension

  
  
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  Tachycardia (beware of patients on β-blockers who may have a normal pulse or bradycardia)

  
  
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  Poor peripheral perfusion

  
  
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  Oliguria

  
  
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  Unexplained metabolic acidosis

  
  
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  High ongoing fluid requirement to maintain blood pressure

Risk Assessment

Most patients with PPH will have no identifying risk factors. The risk factors are stated in Tables 72.1 and 72.2 and may result in direct blood loss or coagulation failure. Other risk factors include the following:

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  Polyhydramnios

  
  
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  Precipitous labor

  
  
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  Augmented labor

  
  
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  High parity

  
  
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  Use of tocolytic agents

  
  
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  Inhalational anesthetics at high concentrations

The most common cause of PPH is uterine atony. At term, blood flow through the placental vasculature is approximately 600 mL/min. After delivery, the primary mechanism that controls blood loss is contraction of the uterine myometrium. This tamponades disrupted blood vessels at the former placental site. Failure of this mechanism can result in massive and rapid blood loss.

Retained placenta is also a common cause of both early and delayed PPH, although not all cases result in significant blood loss. Retained placental fragments may be unrecognized and thus bleeding may be insidious. Patients who have had a prior retained placenta or who deliver well before term are likely to be affected.

Trauma associated with delivery can result in PPH and should be considered in all postpartum patients with continued blood loss despite a firm, contracted uterus. Traumatic bleeding can occur at the following sites:

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  Vagina

  
  
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  Cervix

  
  
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  Uterus (poor handling during cesarean section, disrupted sutures)

  
  
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  Perineum (laceration or episiotomy)

  
  
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  Other structures—tearing of the broad ligament, ovarian artery disruption

Uterine inversion is a rare cause of PPH but can be catastrophic. It should be suspected in any case of PPH when there is significant hypotension.

Implications

Patient outcome depends on early recognition, the rate and severity of blood loss, and timely anesthetic or obstetric intervention. It is worth remembering that PPH is a major cause of morbidity and remains one of the top five causes of maternal death in both developed and developing countries.