In a woman with multiple prior cesarean deliveries and placenta previa, how should placenta accreta spectrum be diagnosed and managed, including imaging, timing of delivery, and surgical approach?

Placenta Accreta Spectrum: Diagnosis and Management

Diagnosis

In a woman with multiple prior cesarean deliveries and placenta previa, placenta accreta spectrum (PAS) should be diagnosed primarily by gray-scale ultrasound with color Doppler, performed by experienced operators, recognizing that the combination of placenta previa overlying a cesarean scar creates an 11% risk of PAS with one prior cesarean—a risk that escalates dramatically with each additional cesarean. 1

Clinical Risk Assessment

• Primary risk stratification: The presence of placenta previa with prior cesarean delivery is the dominant risk factor, present in approximately 49% of PAS cases and in >80% of confirmed accreta cases. 1, 2
• Risk gradient by cesarean number:
  • Placenta previa alone: 3% PAS risk 1
  • Previa + 1 prior cesarean: 11% risk 1
  • Previa + 3 prior cesareans: 7-fold to 56-fold increased risk 3
• Critical principle: Clinical risk factors remain equally important as imaging findings—the absence of ultrasound abnormalities does not exclude PAS. 2, 1

Ultrasound Imaging (First-Line Modality)

• Performance characteristics: Gray-scale ultrasound achieves 90.7% sensitivity (95% CI 87.2–93.6%) and 96.9% specificity (95% CI 96.3–97.5%) for PAS detection. 2, 1

• Key gray-scale findings to identify:

  • Multiple placental lacunae (the most strongly associated finding) 2, 1
  • Loss of the normal hypoechoic retroplacental zone between placenta and myometrium 2, 1
  • Retroplacental myometrial thickness <1 mm 2, 1
  • Disruption or abnormalities at the uterine serosa-bladder interface 2, 1
  • Direct extension of placental tissue into myometrium, serosa, or bladder (suggests percreta) 2, 1

• Color Doppler findings:

  • Turbulent lacunar blood flow (most common Doppler abnormality) 2, 1
  • Increased subplacental vascularity 2, 1
  • Gaps in myometrial blood flow 2, 1
  • Bridging vessels from placenta to uterine margin 2, 1

• Diagnostic limitations: No single ultrasound feature or combination reliably predicts depth of invasion (accreta vs. increta vs. percreta) or distinguishes between grades of PAS. 2, 1

Role of MRI

• Not recommended as initial imaging: MRI should not be the first-line diagnostic modality because its incremental value over ultrasound is uncertain. 1
• Consider MRI selectively for:
  • Posterior placenta previa (difficult to visualize on ultrasound) 2
  • Suspected placenta percreta with potential organ involvement 2
  • Equivocal ultrasound findings requiring clarification 2

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Management Strategy

Delivery Planning and Timing

Women with suspected PAS must be delivered at a Level III or IV maternal care facility with a pre-assembled multidisciplinary team, via planned cesarean hysterectomy at 34 0/7 to 35 6/7 weeks gestation for hemodynamically stable patients. 1, 3

• Rationale for timing: Approximately 50% of patients remaining pregnant beyond 36 weeks require emergent delivery for hemorrhage, making the 34–35 week window optimal for balancing neonatal maturity against maternal hemorrhage risk. 1

• Indications for earlier delivery (<34 weeks):

  • Persistent or heavy vaginal bleeding 1
  • Preeclampsia or other maternal comorbidities 1
  • Onset of labor or rupture of membranes 1
  • Fetal compromise 1

• Antenatal corticosteroids: Administer when delivery is planned before 37 0/7 weeks gestation. 1

Multidisciplinary Team Requirements

• Essential team members must be assembled before delivery:

  • Maternal-fetal medicine physicians 1, 3
  • Experienced pelvic surgeons (gynecologic oncologists preferred for Grade 3E percreta with organ involvement) 1, 3, 4
  • Urologic surgeons when bladder invasion is suspected 1, 3
  • Interventional radiologists 1, 3
  • Obstetric anesthesiologists 1, 3
  • Blood bank with massive transfusion protocols 1, 3
  • Neonatologists 1
  • Intensive care unit capabilities 1, 3

• Facility resource requirements: Delivery at a center lacking these essential resources significantly increases maternal morbidity and mortality. 3

Surgical Approach

The standard operative technique is cesarean hysterectomy with the placenta left in situ after fetal delivery; manual removal of the placenta is strictly contraindicated because it precipitates catastrophic hemorrhage. 1, 5, 3

• Intraoperative principles:

  • Make the uterine incision away from the placenta when feasible 1
  • Consider dorsal lithotomy positioning for optimal pelvic exposure 1
  • Place prophylactic ureteral stents if bladder invasion is anticipated 1
  • Never attempt manual placental removal or forced traction 5, 3

• For Grade 3E percreta with organ involvement:

  • Perform intraoperative cystoscopy to assess bladder invasion 4
  • Consider careful transvaginal ultrasound intraoperatively to determine extent of invasion 4
  • Evaluate whether primary cesarean hysterectomy is safely resectable 4
  • If safe resection is uncertain, consider conservative management with planned delayed hysterectomy at approximately 4 weeks postpartum in stable patients 4

Hemorrhage Management

• Massive transfusion protocol: Transfuse packed red blood cells, fresh-frozen plasma, and platelets in a ratio of 1:1:1 to 1:2:4. 1, 3

• Additional hemorrhage control measures:

  • Consider tranexamic acid to reduce blood loss 3
  • Maintain maternal core temperature >36°C to preserve coagulation factor activity 1, 3
  • Re-dose prophylactic antibiotics if blood loss exceeds 1,500 mL 1
  • Availability of resuscitative endovascular balloon occlusion of the aorta (REBOA) is ideal for Grade 3E disease 4

Pre-operative Optimization

• Anemia correction: Treat anemia during pregnancy with oral or intravenous iron supplementation. 1
• Blood bank notification: Ensure early notification for anticipated large-volume transfusion needs. 1

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Conservative (Uterine-Sparing) Management

• Investigational status: Conservative or expectant management should be considered only for carefully selected cases after thorough counseling; it remains investigational. 1

• Outcomes for placenta percreta managed conservatively:

  • 44% failure rate requiring subsequent hysterectomy 1, 3
  • 17% severe adverse complication rate (sepsis, organ failure, or death) 1, 3
  • 28% infection/febrile morbidity 3
  • 6% severe morbidity including sepsis, organ failure, or death 3

• When to consider: Reserved for fertility desire in select cases or when Grade 3E disease with extensive organ involvement makes primary hysterectomy surgically hazardous. 4, 6

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Pathologic Confirmation and Quality Improvement

• Pathologic diagnosis: PAS is confirmed by absence of decidua basalis with direct placental attachment to or invasion through the myometrium. 2, 3

• Discordance rates: Between 18–29% of clinically diagnosed PAS cases lack histopathologic confirmation after hysterectomy, though many demonstrate uterine wall thinning <3 mm. 1

• Quality improvement: Pathology feedback to radiology and surgery teams is essential for evaluating diagnostic accuracy and management outcomes. 1

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Common Pitfalls and Caveats

• Do not rely solely on imaging: Even with negative ultrasound findings, high clinical risk (previa + prior cesarean) mandates preparation for PAS at delivery. 2, 1

• Avoid manual placental removal: If retained placenta with no plane of separation is encountered, immediately prepare for potential hysterectomy and mobilize the multidisciplinary team. 5

• Do not underestimate percreta: Placenta percreta (Grade 3E) has dramatically worse outcomes than lesser degrees of PAS, with 44% requiring hysterectomy even when conservative management is attempted. 1, 3

• Timing matters: Delaying delivery beyond 36 weeks in suspected PAS carries a 50% risk of emergent delivery for hemorrhage. 1