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Abruptio Placentae - Rule Out

Definition

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Epidemiology

• Complicates approximately 1% of all pregnancies (clinically recognized)
• Incidence peaks between 24-32 weeks of gestation
• If placentas are routinely examined at delivery, subclinical evidence is found in ~4% of cases
• Accounts for approximately 10% of all preterm births
• Abruption sufficient to cause fetal death occurs in ~1 of every 420 deliveries
• Disproportionate increase seen among Black women in the United States

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Pathogenesis

1. Loss of placental surface area for gaseous exchange and fetal nutrition
2. Hematoma expansion causing further dissection
3. Revealed hemorrhage if dissection reaches the placental edge and tracks through the cervix
4. Concealed hemorrhage with circumferential dissection and near-total separation

• Fetal hypoxia and possible fetal death
• Activation of the coagulation cascade -> DIC
• Maternal hypovolemia -> hemorrhagic shock
• Bleeding into myometrium -> Couvelaire uterus (uterine atony, increased hemorrhage risk)

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Risk Factors

Clinical note: After trauma, evidence of abruption may not be apparent for up to 24 hours. Women with vaginal bleeding or contractions post-MVA should be observed for at least 24 hours; asymptomatic patients can be discharged after 6 hours of monitoring.

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Clinical Features

Spectrum of Severity

Classic Triad

• Painful, dark vaginal bleeding (70% of patients)
• Uterine tenderness/pain (~2/3 of patients)
• Uterine contractions/irritability (~1/3 of patients)

Note: About 10% of women present only with occult bleeding (concealed abruption - no external blood loss). Always consider abruption in a patient with uterine pain, fetal distress, or hemodynamic instability even without visible bleeding.

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Diagnostic Approach

Key Points

• Abruption remains a clinical diagnosis - imaging is primarily useful to exclude placenta previa
• Ultrasonography is insensitive - fresh blood is isoechoic to placenta; a normal USS does NOT rule out abruption
• Electronic fetal monitoring (CTG) has 100% negative predictive value for adverse outcomes when reassuring
• MRI is diagnostic but impractical in the acute setting

Investigations

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Differential Diagnosis

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Management

Immediate Stabilization (All Cases)

1. Two large-bore IV access - fluid resuscitation
2. Continuous fetal monitoring (CTG)
3. Emergency obstetric consultation
4. Labs: CBC, metabolic panel, coagulation panel (fibrinogen, FDP), type and cross-match
5. RhoGAM (anti-D Ig 300 μg IM) if mother is Rh-negative
6. Transfuse as needed: PRBCs, FFP, cryoprecipitate (for DIC)

Delivery Decisions

DIC Management

• Coagulopathy develops in ~10% of abruptions, strongly associated with fetal demise or massive hemorrhage
• Use component therapy: FFP (raises fibrinogen ~25 mg/dL per unit), cryoprecipitate (fibrinogen + factors VIII, XIII), platelets
• Target fibrinogen >200 mg/dL

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Maternal and Fetal Complications

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Prevention

• Treat chronic hypertension adequately
• Smoking cessation (dose-response relationship)
• Avoidance of cocaine and substance abuse
• Treat hyperhomocysteinemia with folate supplementation
• Counsel high-risk patients (prior abruption = up to 20-fold recurrence risk) about warning signs

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Key Clinical Pearls for "Rule Out"

"Abruption remains a clinical diagnosis - imaging is useful only to exclude placenta previa." - Creasy & Resnik's Maternal-Fetal Medicine

1. A normal ultrasound does NOT rule out abruption - fresh blood is isoechoic to placenta
2. Concealed abruption can occur with no visible bleeding but significant hemodynamic compromise
3. CTG is the most sensitive tool - 100% NPV for adverse outcomes when reassuring
4. Always consider abruption after trauma, even minor trauma, and observe for at least 6-24 hours
5. Fibrinogen <150 mg/dL indicates severe abruption with active DIC
6. Fetal death occurs in ~15% - risk increases with percentage of placental surface involved

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