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A12. Uterine atony

In normal conditions, the uterus contracts after delivery. A high uterine muscle tone is essential for compressing vessels postpartum, preventing haemorrhage. Uterine atony refers to when the uterine muscle tone is absent. It’s the most common cause of postpartum haemorrhage.

If uncontrolled, it can lead to haemorrhagic shock.

Etiology

  • Overdistension (macrosomia, polyhydramnios, multiple pregnancy)
  • Exhausted myometrium (long labour, excessive use of uterotonics)
  • Chorioamnionitis

Diagnosis and evaluation

The diagnosis is clinical, made based on the presence of postpartum haemorrhage and bimanual examination of the tone of the uterus, which reveals it to be soft. Coagulation status should be evaluated.

Treatment

To prevent uterine atony, oxytocin (a uterotonic) is routinely administered after delivery. However, this routine dose may not be sufficient to prevent it.

In cases where uterine atony is manifest, we have multiple options to stop the bleeding:

  • First line: Give more oxytocin
  • Give prostaglandins (sulprostone, misoprostol)
  • External compression of the uterus (Credé manoeuvre, Fritsch manoeuvre)
  • Manual removal of the placenta
  • Intrauterine balloon tamponade
  • Uterine artery ligation
  • Last line: hysterectomy

If haemorrhage is significant, the patient requires volume replacement therapy or transfusion. Tranexamic acid (an antifibrinolytic) may be used to decrease the bleeding.

Complications

  • Usual complications of heavy bleeding, e.g. haemodynamic instability, shock, death
  • Sheehan syndrome

Sheehan syndrome refers to hypopituitarism due to pituitary ischaemic necrosis following severe postpartum haemorrhage. During pregnancy, the pituitary gland becomes hypertrophic and therefore prone to ischaemia. This may range from mild to life-threatening and may affect any number of pituitary hormones.

The most common presentation is failure to lactate postpartum (due to prolactin deficiency) or amenorrhoea (due to FSH/LH deficiency). Symptoms may present immediately postpartum or even years after delivery. It is diagnosed on MRI. Treatment involves hormone replacement, although prolactin replacement does not yet exist commercially.