placenta abruptio

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abruptio placentae

The premature separation of the placenta from its site of implantation in the endometrium before the delivery of the foetus, commonly known as placental abruption. Some degree of AP occurs in 1:85 deliveries; severe AP with total separation of the placenta is an obstetric emergency seen in 1 in 500–750 deliveries, often accompanied by foetal death.

Clinical findings
Abdominal and/or back pain; irritable, tender or hypertonic uterus; vaginal bleeding (seen in most); 30% are asymptomatic.
Predisposing factors
Pre-eclampsia, eclampsia, chronic hypertension, diabetes, chronic renal disease; mechanical causes are rare (1–5%) and include transabdominal trauma, sudden decompression (as occurs in the delivery of a 1st twin or rupture of membranes in hydramnios) or traction of a short placenta.

Pathophysiology, proposed mechanisms
Local vascular injury of the decidua basalis with bleeding and haematoma formation, which causes shearing of adjacent denuded vessels, exacerbating the bleeding and haematoma; abrupt increased in uterine venous pressure transmitted to intervillous space, resulting in venous bed engorgement and separation of part or the entire placenta.

Expectant therapy if foetus is immature and bleeding limited, treat shock if present; vaginal delivery if possible, or else C-section.

DIC, acute cor pulmonale, renal cortical and tubular necrosis, uterine apoplexy, transfusion hepatitis.

Definable, direct causes that trigger placenta abruptio
Rare (1 to 5%) mechanical factors such as abdominal trauma (for example, from an automobile 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 during pregnancy is associated with up to 18% incidence (however, approximately 50% of placenta abruptio cases severe enough to cause foetal 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 (> 14 drinks per week). The incidence of placenta abruptio, including any amount of placental separation prior to delivery, is about 1 out of 77–89 deliveries; however, the severe form (resulting in foetal death) occurs only in about 1 out of 500–750 deliveries.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

placenta abruptio

Abruptio placentae, see there.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.