Third-Trimester Bleeding: Placental Abruption

PLACENTAL ABRUPTION

Placental abruption refers to an abnormal premature separa-tion of an otherwise normally implanted placenta. There arevarious types of abruption, depending upon the extent and region of separation. A complete abruption occurs when the entire placenta separates. A partial abruption exists when part of the placenta separates from the uterine wall.

Marginal abruption occurs when the separation is lim-ited to the edge of the placenta (Fig. 21.3). A significant abruption requiring delivery occurs in 1% of births.

Abruption occurs when bleeding in the decidua basalis causes separation of the placenta and further bleeding. The classic presentation of abruption is vaginal bleeding with abdominal pain. Smaller or marginal abruptions may pre-sent with bleeding only. Concealed hemorrhage occurs when blood is trapped behind the placenta and is unable to exit. Painful uterine contractions, significant fetal heart rate abnormalities, and fetal demise may occur in severe cases.

Risk factors for placental abruption include chronic hypertension, preeclampsia, multiple gestation, advanced maternal age, multiparity, smoking, cocaine use, preeclamp-sia, and chorioamnionitis. Trauma is also a major risk factor. 

Abruption in a prior pregnancy increases the risk of abrup-tion in subsequent pregnancy by 15- to 20-fold.

An elevated second-trimester maternal serum alpha-fetoprotein (AFP) level may be associated with up to a 10-fold increased risk of placental abruption due to possible entry of AFP into the maternal circulation through the placental uterine interface.

Abruption is often diagnosed by clinical examination, although an ultrasound examination may be useful in less severe cases not requiring immediate delivery. Abruption may occur in the absence of ultrasound findings.

Management of patients with placental abruptionincludes monitoring of vital signs, fluid administration, and delivery for severe hemorrhage. Expectant management may be appropriate for preterm patients with less severe abruptions and minimal bleeding. Delivery is often by cesarean birth. Rarely, blood penetrates the uterus to such an extent that the serosa becomes blue or purple in color. This condition is called Couvelaire uterus. A Kleihauer-Betke or similar test is essential to determine the amount of fetal–maternal hemorrhage. Results guide decisions regarding administration of Rh D immunoglobulin in women who are Rh D-negative and determine the need for blood transfusion in the potentially anemic neonate. Coagulation abnormalities may also be associated with abruption (see Table 21.1). Abruption is the most com-mon cause of coagulopathy in pregnancy. Platelet counts may be low and prothrombin time and partial thrombo-plastin time may be increased. Serum fibrinogen may also be depleted. Disseminated intravascular coagulation is a rare but extremely serious complication.