Reproductive · Obstetric Emergencies
The facts most likely to be tested
The classic clinical presentation of placental abruption is painful vaginal bleeding associated with uterine tenderness and hypertonicity.
Maternal hypertension (chronic or gestational) and tobacco use are the most significant modifiable risk factors for placental abruption.
Cocaine use is a classic board-tested risk factor due to its ability to induce vasoconstriction and placental ischemia.
Placental abruption is a clinical diagnosis; ultrasound is often used to rule out placenta previa but has low sensitivity for detecting an abruption.
Couvelaire uterus is a life-threatening complication where blood infiltrates the myometrium, resulting in a firm, blue-toned uterus.
Disseminated intravascular coagulation (DIC) is the most common severe maternal complication due to the release of tissue factor from the retroplacental clot.
Management of a stable fetus with a mild abruption involves expectant management and fetal monitoring, whereas fetal distress or maternal instability requires emergent cesarean delivery.
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A 28-year-old G2P1 woman at 34 weeks gestation presents to the emergency department with sudden-onset, severe abdominal pain and dark red vaginal bleeding. She has a history of poorly controlled chronic hypertension and admits to recent cocaine use. On physical examination, the uterus is firm, tender to palpation, and exhibits frequent, high-amplitude contractions. Fetal heart rate monitoring reveals recurrent late decelerations. The patient's blood pressure is 160/95 mmHg.
What is the most likely diagnosis?
Placental abruption
The patient presents with the classic triad of painful vaginal bleeding, uterine tenderness, and hypertonicity, with significant risk factors including hypertension and cocaine use, which points directly to placental abruption.
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High yield triage
Etiology / Epidemiology
Primary risk factor is maternal hypertension (chronic or preeclampsia). Other triggers include trauma and cocaine use.
Clinical Manifestations
Classic triad: painful vaginal bleeding, port-wine stained amniotic fluid, and uterine hypertonicity.
Diagnosis
Diagnosis is clinical. Transabdominal ultrasound is used to rule out placenta previa, but has low sensitivity for abruption.
Treatment
Immediate delivery is the definitive treatment. Avoid tocolytics if fetal distress or maternal instability is present.
Prognosis
High risk of DIC and fetal demise. Maternal mortality is rare but fetal mortality reaches 20-35%.
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Epidemiology & Etiology
The most significant risk factor is maternal hypertension (chronic or gestational). Other high-yield associations include smoking, cocaine use, and prior history of abruption. Abdominal trauma (e.g., motor vehicle accident) is a classic board-tested precipitant.
Pertinent Anatomy
The placenta is a vascular organ attached to the uterine wall. Premature separation disrupts the uteroplacental interface, leading to hemorrhage between the placenta and the decidua basalis.
Pathophysiology
Rupture of maternal vessels in the decidua basalis leads to hematoma formation. This hematoma causes mechanical separation of the placenta, resulting in fetal hypoxia and maternal blood loss. The release of tissue factor into maternal circulation can trigger disseminated intravascular coagulation (DIC).
Clinical Manifestations
Patients present with painful vaginal bleeding and a rigid, tender uterus. The uterus may feel board-like on palpation. Fetal bradycardia or non-reassuring heart rate patterns are common. Maternal hypotension and tachycardia suggest significant concealed hemorrhage.
Diagnosis
Diagnosis is primarily clinical. Transabdominal ultrasound is mandatory to exclude placenta previa, though it misses up to 50% of abruptions. Kleihauer-Betke test may be used to quantify fetomaternal hemorrhage for Rh-negative patients.
Treatment
Management depends on gestational age and fetal status. Immediate delivery is indicated for fetal distress or maternal instability. Avoid tocolytics as they may mask signs of labor. Corticosteroids are indicated if the fetus is <34 weeks and stable.
Prognosis
Major complications include DIC, hypovolemic shock, and couvelaire uterus (blood infiltration into the myometrium). Continuous fetal heart rate monitoring is required for stable patients to detect sudden deterioration.
Differential Diagnosis
Placenta Previa: painless, bright red bleeding
Vasa Previa: fetal distress immediately following membrane rupture
Uterine Rupture: loss of fetal station and cessation of contractions
Cervical Insufficiency: painless dilation without bleeding
Bloody Show: minimal bleeding associated with labor onset