abruptio placentae

**Definition:** Premature detachment of a normally located placenta from the decidua basalis before delivery of the fetus, typically after 20 weeks' gestation.

**Pathophysiology:** Rupture of maternal decidual spiral arteries leads to retroplacental hemorrhage (hematoma), which dissects and separates the placenta. Chronic placental ischemia and vasculopathy (hypertension, preeclampsia) are the main underlying mechanisms. Acute causes include shearing forces (trauma, rapid uterine decompression after membrane rupture in polyhydramnios or delivery of a first twin). Cocaine causes vasoconstriction.

**Risk factors (high-yield):** - Maternal hypertension (chronic or preeclampsia): the most common associated condition - Abdominal trauma (motor vehicle collision, intimate partner violence) - Cocaine use and cigarette smoking - Prior abruption (the strongest risk factor for recurrence, ~10-15x) - Advanced maternal age, multiparity - PPROM, chorioamnionitis, polyhydramnios, multiple gestation - Thrombophilias

**Clinical features:** - Painful vaginal bleeding in the third trimester, often dark blood - Abdominal or back pain, a firm, rigid ("woody") tender uterus, and uterine hypertonicity or frequent contractions - Fetal distress (non-reassuring tracing, late decelerations, bradycardia) or fetal demise - Concealed abruption: blood trapped behind the placenta, so there may be little or no visible bleeding despite significant hemorrhage - Couvelaire uterus: blood extravasates into the myometrium, giving a purple/blue discoloration of the uterine wall

**Diagnosis:** Mainly clinical. Ultrasound is insensitive (it may show a retroplacental clot but is often normal), so a negative ultrasound does NOT rule out abruption. Obtain a CBC, coagulation studies, fibrinogen (low fibrinogen predicts severe abruption), type and crossmatch, and a Kleihauer-Betke test if the mother is Rh-negative. Avoid digital vaginal exam until placenta previa has been excluded.

**Differential: Abruption vs. placenta previa** - Abruption: painful bleeding, tender hypertonic uterus, normal placental location, associated with HTN/cocaine/trauma - Previa: PAINLESS bright red bleeding, soft relaxed uterus, placenta covers the cervical os (diagnosed by ultrasound) - Vasa previa: painless bleeding at membrane rupture with fetal bradycardia or a sinusoidal tracing (fetal blood loss) - Uterine rupture: sudden pain, loss of fetal station, prior C-section or uterine surgery

**Complications:** - Maternal: hemorrhagic shock, DIC (release of tissue thromboplastin into the circulation), acute kidney injury, Sheehan syndrome, need for transfusion or hysterectomy - Fetal: hypoxia, preterm birth, growth restriction, stillbirth - Rh-negative mothers: fetomaternal hemorrhage, so give RhIG

**Management:** - Stabilize the mother: two large-bore IVs, fluids, blood products, and monitoring of coagulation - Unstable mother or non-reassuring fetal status: emergent delivery (usually cesarean; vaginal delivery is acceptable if rapid and the fetus is stable or dead) - Stable mother, term (≥37 weeks): deliver, usually vaginally - Stable mother, preterm with a reassuring fetus: close monitoring, with antenatal corticosteroids for lung maturity before 34 weeks - Fetal demise with a stable mother: vaginal delivery and correction of coagulopathy - Tocolytics are generally contraindicated.

**Buzzwords:** painful third-trimester bleeding, tetanic/hypertonic uterus, cocaine, hypertension, DIC, Couvelaire uterus, retroplacental hematoma.