Diagnosis

The symptoms and signs of placental abruption vary enormously. Even the absence of ultrasound identification does not rule out a life-threatening placental abruption.

In classical extreme, profuse abruption, pain, shock, uterine rigidity and absent fetal heart sounds are evident. Consumptive coagulopathy - hypofibrinogenaemia of less than 150mg/dL, renal failure and uteroplacental apoplexy - extravasation of blood into the uterine musculature and serosa - are rarer signs.

In milder cases, the following symptoms and signs can occur singly, in combination, or none may be present at all:

• vaginal bleeding
• uterine tenderness and back pain
• fetal distress
• high frequency uterine contractions of low tone
• idiopathic preterm labour
• hypotension leading to rapid shock

The differential diagnosis is that of other causes of vaginal bleeding in the third trimester, and so it is often principally necessary to rule out placenta praevia by clinical inspection and ultrasound. Unfortunately, and contrary to popular belief, abruption and placenta praevia may both present with or without pain.