A9. Placental abruption. Pathomechanism, diagnosis, differential-diagnosis

Placental abruption refers to when the placenta separates from the uterus prematurely, sometime before the second stage of labour, but typically sometime in the second half of pregnancy. This leads to a retroplacental bleeding which may range from small and asymptomatic to severe and life-threatening. It is one of the life-threatening causes of vaginal bleeding in this half of the pregnancy, and so recognising it early is important.

Abruption may be partial or complete.

Etiology

• Hypertension
• Abdominal trauma
• Smoking
• Previous placental abruption

Pathomechanism

The immediate cause of placental abruption is rupture of maternal vessels in the decidua, either arteries or veins. The vascular rupture causes haemorrhage which splits the decidua, separating it from the placenta.

In most cases, there is a chronic pathological process of the placental vasculature which causes the rupture of blood vessels. In other cases, for example in case of trauma, the trauma directly causes blood vessels to rupture.

Classification

Abruption is classified according to Sher’s classification:

• Grade I – mild, no vaginal bleeding, often discovered after delivery
• Grade II – tense, tender abdomen, moderate vaginal bleeding, live foetus
• Grade III – foetal demise
  • Grade IIIA – without coagulopathy
  • Grade IIIB – with coagulopathy

Clinical features

Symptoms of placental abruption include vaginal bleeding, abdominal or back pain, uterine tenderness, and contractions. However, the pain may range from mild cramping to severe. Vaginal bleeding may be small despite a large amount of blood loss, as blood may be retained behind the placenta. CTG may be abnormal. In case of severe abruption (>50% placental separation), disseminated intravascular coagulation is common.

Diagnosis and evaluation

The diagnosis is clinical, based on clinical features. However, ultrasound can assist the diagnosis and can show a retroplacental clot. Ultrasound can, however, not rule out abruption, as it’s not sensitive.

Differential diagnosis

Differential diagnosis includes other causes of late pregnancy vaginal bleeding. See the previous topic.

Treatment

Initial management involves assessing maternal and foetal stability, and stabilisation if necessary. Blood transfusion and fluids may be necessary. Tranexamic acid may be used to limit bleeding.

Definitive management of placental abruption is delivery. In most cases of grade II abruption this is emergency C-section. If abruption occurs during the second stage of labour, expedited operative vaginal delivery is performed. In case of grade III abruption, vaginal delivery is preferred.

Complications

• Haemodynamic instability
• Shock
• Foetal distress or demise