Placental Abruption

Introduction

• Description: Placental abruption is the premature separation of an otherwise normally implanted placenta before the delivery of the fetus. The term is generally applied only to 20-week or later gestations.

• Prevalence: 1/185–290 deliveries; sufficient to result in fetal death, 2–10/1000 deliveries (approximately 10% of third-trimester fetal demise).

• Predominant Age: Reproductive age.

• Genetics: No genetic pattern.

Etiology and Pathogenesis

• Causes: Pregnancy-induced hypertension (most common), trauma to the abdomen, decompression of an overdistended uterus (loss of amniotic fluid, delivery of a twin), cocaine use. It is thought that abnormalities in the early development of the spiral arteries lead to decidual necrosis, placental inflammation, and infarction, resulting in vascular disruption and bleeding.

• Risk Factors: Pregnancy-induced hypertension (most common, 5-fold increased risk over those with normal blood pressure). Prior abruption: 15% chance if one prior episode, 20%–25% for two or more prior events. Others: smoking more than 1 pack/day (2.5-fold increased risk; risk increases by 40% for each pack/day smoked), multiparity, alcohol abuse, cocaine use, polyhydramnios, maternal hypertension (5-fold increased risk), premature rupture of the membranes, external trauma, uterine leiomyomata or anomalies, increased age or parity, and multiple gestation.

Signs and Symptoms

• Highly variable

• Vaginal bleeding (not universal; approximately 80%)

• Abdominal, back, or uterine pain (65%)

• Fetal bradycardia or late decelerations (60%)

• Uterine irritability, tachysystole, tetany, elevated baseline intrauterine pressure (20%–40%, thrombin is a strong uterotonic)

• Maternal hypotension or signs of volume loss (postural hypotension, shock)

• Fetal demise

Diagnostic Approach