Placental Abruption

Risk factors

• Hypertensive disorders (chronic HTN, preeclampsia) — strongest modifiable risk factor
• Prior abruption (10-15% recurrence)
• Cocaine, methamphetamine use
• Smoking
• Trauma (motor vehicle accident, fall, intimate partner violence) — even minor
• Rapid uterine decompression (rupture of membranes with polyhydramnios, delivery of first twin)
• Premature rupture of membranes, chorioamnionitis
• Advanced maternal age, multiparity
• Thrombophilia

Pathophysiology

Vascular disruption at the decidual-placental interface produces a retroplacental hematoma that expands and dissects further placental separation. Concealed hemorrhage with hematoma can extravasate into myometrium (Couvelaire uterus). Thromboplastin release into maternal circulation activates the coagulation cascade → DIC (occurs in up to 20% of severe abruptions).

Clinical presentation

Differential diagnosis

• Placenta previa — Painless bright red bleeding, soft uterus
• Uterine rupture — Severe pain, loss of fetal station, fetal bradycardia; usually with prior uterine surgery
• Vasa previa — Fetal vessels rupture with membrane rupture; fetal blood loss
• Preterm labor — Regular contractions with cervical change; bleeding may be present (bloody show)
• Chorioamnionitis — Fever, uterine tenderness, fetal tachycardia; PROM history
• Trauma without abruption — Trauma can cause abruption hours later; observe with continuous monitoring 4-24 hours

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Third-trimester bleeding<br/>± pain] --> B[Avoid digital exam<br/>until previa excluded]
  B --> C[Ultrasound +<br/>continuous fetal monitoring<br/>+ labs incl coags]
  C --> D{Diagnosis?}
  D -->|Previa on US| E[Manage as previa]
  D -->|Abruption suspected<br/>clinical| F[Hemodynamic status?]
  F -->|Unstable or<br/>nonreassuring FHR| G[Emergent cesarean<br/>+ resuscitation<br/>+ blood products]
  F -->|Stable, reassuring| H{Gestational age}
  H -->|≥36 weeks| I[Deliver — vaginal<br/>if labor progressing]
  H -->|<36 weeks| J[Hospitalize, corticosteroids,<br/>close monitoring]
  J --> K{Worsening?}
  K -->|Yes| G
  K -->|No| L[Deliver at 36-37 weeks<br/>or sooner if change]

Treatment

Complications

• Maternal: hypovolemic shock, DIC, acute kidney injury, Couvelaire uterus, postpartum hemorrhage, hysterectomy, Sheehan syndrome, death
• Fetal: hypoxia, IUGR (chronic abruption), preterm birth, stillbirth (~12% perinatal mortality with significant abruption)
• Neonatal: birth asphyxia, anemia
• Recurrence in subsequent pregnancies (~10-15%)

PANCE pearls

• Placental abruption is a CLINICAL diagnosis — ultrasound has low sensitivity (~25-50%); negative imaging does NOT rule it out.
• Concealed abruption can present with disproportionate maternal hemodynamic compromise relative to visible bleeding; suspect when hypotension exceeds expected blood loss.
• All pregnant trauma patients require ≥4 hours of continuous fetal monitoring (24 hours if abnormal); abruption can present hours after the initial event.
• DIC complicates ~10-20% of severe abruptions; fibrinogen levels are the best marker — pregnant women normally have elevated fibrinogen, so a 'normal' value of 200 may already represent significant consumption.
• Couvelaire uterus (uterine apoplexy with bluish discoloration from blood extravasation into myometrium) does not necessarily require hysterectomy — manage based on hemostasis.
• Cocaine and methamphetamine use cause vasoconstriction-mediated abruption — assess for substance use in unexplained abruptions.
• Painful dark bleeding with tense tender uterus = abruption; painless bright red bleeding with soft uterus = previa.

References

• ACOG PB 234 — ACOG Practice Bulletin No. 234: Prediction and Prevention of Spontaneous Preterm Birth (related guidance)
• ACOG CO 518 — ACOG Committee Opinion 518: Intimate Partner Violence (relevant trauma risk)
• Ananth 2006 — Placental Abruption and Adverse Perinatal Outcomes (Ananth and Wilcox, Am J Epidemiol 2006)