Placental Abruption

Placental abruption is premature separation of the placenta from the decidua after 20 weeks of gestation. The usual initiating event is rupture of maternal vessels in the decidua. Blood collects behind the placenta, forming a retroplacental haematoma that pushes the placenta away from the uterine wall. As separation increases, the area available for maternal–fetal gas and nutrient exchange decreases. The uterus may become painful, firm, and hypertonic because blood irritates the myometrium and stimulates contractions. The same bleeding can remain trapped behind the placenta, so the amount seen on a pad may be surprisingly small. That mismatch is dangerous: external bleeding does not reliably measure the severity of an abruption. A patient with little visible blood may already have substantial concealed haemorrhage, impaired placental exchange, or developing shock. Severe abruption can also release tissue-factor activity and consume clotting factors, leading to disseminated intravascular coagulation (DIC). The maternal and fetal consequences develop together. Maternal blood loss reduces perfusion; placental separation reduces fetal oxygen delivery. A non-reassuring fetal heart rate may therefore be the first visible sign that the separation is extensive....