In a pregnant woman with risk factors such as prior cesarean delivery, placenta previa, previous uterine surgery, or advanced maternal age, how should placenta accreta spectrum be diagnosed and managed, including recommended imaging, timing of delivery, surgical approach, and intra‑operative measures to control hemorrhage?

Placenta Accreta Spectrum: Diagnosis and Management

Risk Assessment and Clinical Context

Women with placenta previa overlying a prior cesarean scar face the highest risk for placenta accreta spectrum (PAS), and this combination is present in 49% of all PAS cases. 1, 2

The risk escalates dramatically with multiple cesarean deliveries:

• 3% risk with placenta previa alone 1, 2
• 11% risk with placenta previa plus one prior cesarean 1, 2
• 40% risk with two prior cesareans 2
• 61% risk with three prior cesareans 2
• 67% risk with five or more prior cesareans 2

Additional risk factors include advanced maternal age, multiparity, prior uterine surgery (curettage, Asherman syndrome), and in-vitro fertilization. 1, 3

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Diagnostic Imaging Strategy

Primary Imaging Modality

Gray-scale ultrasound is the first-line diagnostic tool, with pooled sensitivity of 90.7% and specificity of 96.9% for detecting PAS. 1, 2

Key ultrasound findings to identify:

• Multiple placental lacunae (most strongly associated finding) 1, 2
• Loss of the normal hypoechoic retroplacental zone 1, 2
• Retroplacental myometrial thickness < 1 mm 4, 1
• Thinning or disruption of the hyperechoic uterine serosa-bladder interface 1, 2
• Direct extension of placental tissue into myometrium, serosa, or bladder (suggests percreta) 1

Color Doppler findings:

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

Critical Diagnostic Caveat

The absence of ultrasound abnormalities does NOT exclude PAS—clinical risk factors remain equally important as imaging findings. 4, 1, 2 Interobserver variability is substantial, and many ultrasound features associated with PAS also appear in normal placentas without PAS. 4, 2

Role of MRI

MRI is NOT recommended as the initial imaging modality because its incremental diagnostic value over ultrasound alone is uncertain. 4, 1

Consider MRI only in specific scenarios:

• Posterior placenta previa (difficult to visualize on ultrasound) 1
• Suspected placenta percreta requiring surgical planning 1
• Equivocal ultrasound findings 1

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Management: Delivery Planning and Timing

Facility and Team Requirements

All women with suspected PAS must deliver at a Level III or IV maternal care facility with a multidisciplinary team experienced in PAS management. 4, 1, 2, 3 Delivering at a center lacking essential resources—blood bank, coordinated team, and ICU support—significantly increases maternal morbidity and mortality. 3

Required multidisciplinary team members:

• Maternal-fetal medicine subspecialists 1, 2, 3
• Experienced pelvic surgeons (gynecologic oncologists for grade 3 percreta) 1, 3, 5
• Urologic surgeons (when bladder involvement suspected) 1, 3, 5
• Interventional radiologists 1, 2, 3
• Obstetric anesthesiologists 1, 2, 3
• Blood bank with massive transfusion protocols 1, 2, 3
• Neonatologists and intensive care capabilities 1, 3

Optimal Delivery Timing

Planned cesarean delivery should occur at 34 0/7 to 35 6/7 weeks gestation for hemodynamically stable patients. 4, 1, 2, 3 This timing balances neonatal maturity against maternal hemorrhage risk, as approximately 50% of women with PAS who remain pregnant beyond 36 weeks require emergent delivery for hemorrhage. 1, 2

Earlier delivery is required for:

• Persistent bleeding 4
• Preeclampsia 4
• Labor or rupture of membranes 4
• Fetal compromise 4
• Developing maternal comorbidities 4

Administer antenatal corticosteroids when delivery is planned before 37 0/7 weeks. 1

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Surgical Approach and Intra-operative Management

Standard Operative Technique

The standard approach 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, 2, 3, 5

Intra-operative surgical principles:

• Make the uterine incision away from the placenta when feasible 1
• Consider dorsal lithotomy positioning for optimal pelvic exposure 1
• Place prophylactic ureteric stents if bladder invasion is anticipated 1, 5
• Never attempt manual placental removal 1, 2, 3

Hemorrhage Control Measures

In massive hemorrhage, transfuse packed red blood cells, fresh frozen plasma, and platelets in a ratio of 1:1:1 to 1:2:4. 4, 1

Additional hemorrhage control strategies:

• 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 5
• Consider intra-operative uterine artery embolization combined with tranexamic acid in high-risk cases 5

Pre-operative Optimization

Correct anemia during pregnancy with oral or intravenous iron supplementation. 1 Ensure early notification of the blood bank for anticipated large-volume transfusion needs. 1

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Special Consideration: Placenta Percreta with Organ Involvement

For grade 3E disease (placenta percreta) with suspected bladder, cervical, or parametrial invasion, intra-operative assessment must include:

• Gross surgical field exposure and examination 5
• Cystoscopy 5
• Consideration of careful intra-operative transvaginal ultrasound to determine extent of placental invasion 5

If safe resection is uncertain, consider conservative management with planned delayed hysterectomy at approximately 4 weeks post-cesarean delivery in stable patients. 5 This approach requires careful patient selection and counseling.

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Conservative (Uterine-Sparing) Management

Conservative management is considered investigational and should be offered only after thorough counseling regarding uncertain benefits and substantial risks. 4, 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 1, 3
• 6% severe morbidity including sepsis, organ failure, or death 1, 3

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Pathologic Confirmation and Quality Improvement

Pathologic diagnosis requires absence of decidua basalis with direct placental attachment to or through the myometrium. 4, 1, 3 Between 18–29% of clinically diagnosed PAS cases lack histopathologic confirmation after hysterectomy, though many demonstrate uterine wall thinning < 3 mm. 1

Pathology feedback to radiology and surgery is essential for quality-improvement initiatives and evaluating management outcomes. 1