Placenta abruptio

Alternative names:

ablatio placentae; abruptio placentae; accidental hemorrhage; premature separation of placenta

Definition:

The separation of the placenta from the site of uterine implantation before delivery of the fetus.

Causes, incidence, and risk factors:

It is frequently difficult to determine the exact causes of placenta abruptio. Definable, direct causes that trigger placenta abruptio are quite rare (1 to 5%). They include mechanical factors such as abdominal trauma (for example, from an auto accident or fall), sudden loss in uterine volume as occurs with rapid loss of amniotic fluid or the delivery of a first twin, or an abnormally short umbilical cord (usually only a problem at the time of delivery).

Predisposing factors include the following risk factors: a past medical history of placenta abruptio (after 1 prior episode there is a 10 to 17% recurrence, after 2 prior episodes the incidence of recurrence exceeds 20%); hypertension or high blood pressure during pregnancy is associated with 2.5 to 17.9% incidence (however, approximately 50% of placenta abruptio cases severe enough to cause fetal death are associated with hypertension); increased maternal age; increased number of prior deliveries; increased uterine distention (as may occur with multiple pregnancies or abnormally large volume of amniotic fluid); diabetes mellitus in the pregnant woman; cigarette smoking; and drinking alcohol during pregnancy (more than 14 drinks per week).

The incidence of placenta abruptio, including any amount of placental separation prior to delivery, is about 1 out of 77 to 89 deliveries. However, the severe form (resulting in fetal death) occurs only in about 1 out of 500 to 750 deliveries.