Placental abruption is defined as premature placental separation, and it occurs in around 1% of pregnancies. Major degrees of abruption have an incidence of 0.2%, with a perinatal mortality of 50%.
Risk factors for abruption are a previous history of abruption, an overdistended uterus (twins, polyhydramnios), pre-eclampsia, multiparity, greater maternal age, smoking, trauma and use of drugs such as cocaine and amphetamines.
Problems and special considerations
The diagnosis of abruption is clinical, supported by ultrasound. The usual presentation is of bleeding in the third trimester which, unlike the differential diagnosis of placenta praevia, is associated with abdominal pain due to uterine distension. The uterus commonly starts contracting, and this will exacerbate the underlying pain. Cardiotocography may show evidence of fetal compromise in the form of loss of fetal heart rate variability, decelerations or bradycardia. Minor degrees of abruption may be diagnosed retrospectively after an uneventful delivery. Abruption that is retroplacental, as opposed to at the edge of the placenta, may be concealed; if severe, these patients may present with a hard, tense abdomen, hypovolaemic shock and even disseminated intravascular coagulation.
It is easy to underestimate blood loss in abruption, especially if the membranes have not ruptured, since much of the bleeding will be concealed. Cardiovascular changes occur late, probably because of the sympathetic activity engendered by abdominal pain and because patients are generally young and fit.
Coagulopathy is an early development in placental abruption, since coagulation factors are rapidly consumed by the intrauterine clot. Where abruption is severe enough to cause fetal death, the risk is as high as 50%. The risk of amniotic fluid embolism is also thought to be increased, especially in severe cases.
Management options
Management is dependent on whether the fetus is still alive at presentation, and on the condition of the mother. If there is no evidence of placental insufficiency, then the mother may be allowed to labour, with careful fetal and maternal monitoring. Basic fluid resuscitation is essential, and platelet count, coagulation tests and fibrin degradation products should be measured on admission and at regular intervals. Regional analgesic techniques are not contraindicated, but normovolaemia and unimpaired coagulation are of paramount importance if they are used. Blood should be cross-matched and available. Early artificial rupture of the membranes may reduce the risk of coagulopathy and amniotic fluid embolism.
When the fetus has already died, then vaginal delivery is the technique of choice. Particular attention should be paid to the risk of coagulopathy.
Caesarean section
Caesarean section is indicated if there is fetal or maternal compromise. As with placenta praevia, general anaesthesia is the method of choice in the mother with cardiovascular decompensation, and should also be used in the presence of clotting disorders (see Chapter 71, Abnormal placentation). If an epidural catheter is already in situ, then this may be used to provide anaesthesia unless there are major contraindications. Unlike placenta praevia, where the mother may be put at risk if caesarean section is carried out before blood is available, there are benefits for both fetus and mother in operating without delay in the case of abruption: coagulopathy may be prevented and the risk of causing massive bleeding by having to cut through the placenta is not an issue.
After delivery
Postpartum haemorrhage is far more common following abruption. This may arise as a result of coagulopathy or because the uterus fills with blood and cannot contract (Couvelaire uterus).
Key points
• Blood loss may be underestimated in abruption.
• Coagulopathy is common.
• Caesarean section should not be delayed once the mother has been resuscitated.
• Regional anaesthesia may be used in the absence of hypovolaemia or impaired coagulation.
Further reading
Oyelese Y, Ananth CV. Placental abruption. Obstet Gynecol 2006; 108: 1005-16.
Tikkanen M. Placental abruption: epidemiology, risk factors and consequences. Acta Obstet Gynecol Scand 2011; 90: 140-9.