USMLE Prep - Medical Reference Library

Placenta Accreta Spectrum — Antenatal Planning & Delivery

System: Obstetrics Gynecology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

PAS requires antenatal diagnosis with targeted ultrasound ± MRI, delivery planning at Level III/IV center, and multidisciplinary approach; cesarean hysterectomy with placenta in situ is standard for accreta/increta/percreta.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Placenta Accreta Spectrum Antenatal Planning Delivery, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CBC (Baseline hematology), BMP (Electrolytes/renal). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Analgesia/Antipyretics. Use validated frameworks (e.g., Team & Preparation) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Management Notes

Placental removal attempts are dangerous—avoid. Ensure neonatal team present for late preterm delivery.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

Team & Preparation

DomainPlan
Timing34–35⁶⁄₇ weeks, no labor
Blood productsMassive transfusion ready
Surgical teamMFM, GynOnc, anesthesia, urology
AdjunctsBalloon catheters/REBOA in select centers
CounselingHysterectomy, fertility loss

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
AcetaminophenAnalgesic/antipyreticHoursSymptom control as appropriateHepatotoxicity (overdose)
Ondansetron5-HT3 antagonismMinutesAntiemesis if neededQT prolongation

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

References

  1. SMFM/ACOG PAS Consult — Link