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Placenta Praevia & Placenta Accreta Spectrum (PAS): Consolidated Guideline

Table of Contents

1) Scope & Definitions

  • Placenta praevia: Placenta overlying or abutting the internal cervical os.
  • Low-lying placenta: Placental edge close to but not covering the os (distance definition varies by society; plan using exact TVUS measurement).
  • Placenta accreta spectrum (PAS): Abnormal adherence/invasion—accreta (adherent), increta (into myometrium), percreta (through serosa ± adjacent organs).

2) Risk Stratification (Book at 1st Scan; Update at Anomaly Scan)

  • High-risk for PAS: Prior cesarean section (risk rises with number), placenta praevia over a scar, prior uterine surgery, advanced maternal age (AMA), and IVF.
  • Flag high-risk cases for targeted imaging and delivery planning in a specialist centre.

3) Imaging & Surveillance

Modality

  • Transvaginal ultrasound (TVUS) is safe and remains the gold standard to define placental–os distance in suspected praevia or low-lying placenta.
  • Add color Doppler when PAS is suspected.

Schedule

  • If low-lying/previa at the mid-trimester scan → repeat TVUS at ~32 weeks, and again at 36–37 weeks to finalize delivery planning.
  • Local ultrasound access may warrant earlier reviews after bleeding episodes.
  • PAS suspicion (risk factors or signs): targeted US by experienced operator ± MRI to define depth and extra-uterine extent (mainly for posterior or bladder involvement).

Key PAS Sonographic Signs (Document Explicitly)

  • Multiple placental lacunae
  • Loss of clear zone
  • Myometrial thinning
  • Bridging vessels/hypervascularity
  • Uterine–bladder interface abnormalities

4) Antepartum Management (Praevia ± PAS)

General

  • Avoid digital cervical examinations.
  • Manage any bleeding as antepartum hemorrhage (APH): IV access, crossmatch, steroids if preterm risk, and anti-D if Rh-negative.
  • Consider tocolysis only to facilitate steroids or transfer—not for long-term prolongation.
  • Counsel on warning signs; advise pelvic rest.
  • Admit for significant or recurrent bleeding, or if access to emergency care is limited.

Transfer & Place of Care

  • PAS or high-risk praevia: Plan care and delivery in a Level III/IV centre of excellence with MFM, anesthesia, urology, interventional radiology, blood bank (MTP), and ICU/NICU.

5) Timing & Mode of Delivery

Placenta Praevia / Persistent Low-Lying

  • Elective cesarean once fetal maturity and bleeding risk are balanced.
    • Stable, no major bleeding: 37+0–37+6 weeks (per JOGC and others).
    • Recurrent/ongoing bleeding or additional risks: 36+0–36+6 weeks (or earlier for acute events).
  • A final TVUS at 36–37 weeks to map placental edge and cord insertion; plan incision to avoid placenta.
  • Trial of labor may be considered only when the placental edge is clearly away from the os (per local threshold/policy) and immediate cesarean capability exists.

PAS (Suspected/Confirmed)

  • Planned delivery (no labor/bleeding): typically 34+0–35+6 weeks after corticosteroids, individualized by centre and disease extent; earlier if bleeding or labor begins.
  • Preferred strategy: Cesarean hysterectomy with placenta left in situ (no attempt at removal).
  • Prepare for massive hemorrhage with multidisciplinary readiness.

6) Pre-Operative Checklist (Praevia & PAS)

  • Team: Lead obstetric surgeon (senior), MFM, senior anesthetist, neonatology; for PAS add urology, IR/vascular, theatre nursing, and blood bank lead.
  • Blood: Group & save, cross-match, activate MTP, cell salvage if available; TXA on induction or after cord as per local PPH bundle.
  • Imaging: Map included in notes; mark suspected placental upper margin.
  • Urology: Cystoscopy or ureteric stents only case-by-case (no universal benefit).
  • Neonatal: Steroids (and magnesium if <32 weeks for neuroprotection).
  • Consent: Discuss risks—haemorrhage, transfusion, hysterectomy (PAS), bladder/ureter/bowel injury, ICU stay.

7) Intra-Operative Strategy

Placenta Praevia (No PAS)

  • Entry: Midline or Pfannenstiel per maternal habitus/complexity.
  • Uterine incision: Choose site to avoid transecting placenta (intraoperative US guidance helpful). Be prepared for classical or high transverse incision.
  • Haemorrhage control: Uterotonics, balloon tamponade, compression sutures, uterine/iliac ligation, TXA; escalate per PPH protocol.
  • Interventional radiology embolization if available.

PAS (Core Principles)

  • Do not attempt placental removal.
  • Deliver fetus via incision distant from placenta → close uterus around placenta in situ, then proceed to total or supracervical hysterectomy as planned.
  • Dissection: Develop avascular planes; watch bladder pillars; call urology early if cystotomy risk or percreta suspected.
  • Adjuncts (select centres): REBOA/balloon occlusion catheters, IR standby, staged procedures under institutional PAS protocol.

8) Conservative / Uterus-Sparing Options in PAS (Selected Cases Only)

  • Options: Leaving placenta in situ with delayed hysterectomy, partial uterine resection, or uterine devascularization ± adjuvants.
  • Require strict selection, MDT oversight, informed consent, and close imaging follow-up.
  • Counsel regarding higher risks: secondary haemorrhage, infection, re-intervention.

9) Postpartum Care

  • Monitoring: HDU/ICU with serial Hb/coagulation checks; watch for secondary PPH or infection.
  • Thromboprophylaxis: Begin once bleeding is controlled.
  • If placenta left in situ: Clinical + US/MRI surveillance; counsel on red flags (bleeding, fever, pain).
  • Future pregnancies: High recurrence and previa risk—advise early MFM referral.

10) Documentation & Audit (Record Every Time)

  • Exact placental–os distance and side, cord insertion, PAS signs.
  • Team members, time of MTP activation, EBL/QBL, transfusion units, procedures performed, complications, neonatal outcomes.
  • Use a local PAS/praevia proforma for quality audit.

11) Quick-Reference: Suggested Timings (Stable Mother–Fetus)

ConditionPlanTiming
Persistent placenta praevia without major bleedingElective CS37+0–37+6 weeks
Placenta praevia with recurrent bleeding/risksElective CS36+0–36+6 weeks
PAS (suspected/confirmed), stablePlanned delivery in Level III/IV centre (often CS-hysterectomy)34+0–35+6 weeks

12) Source Backbone

  • RCOG Green-top 27a: Placenta Praevia & Placenta Accreta—Diagnosis & Management.
  • JOGC Guideline No. 402 (2020): Diagnosis & Management of Placenta Previa.
  • ACOG/SMFM Obstetric Care Consensus No. 7 (2018, reaffirmed): Placenta Accreta Spectrum.
  • FIGO Consensus Guidelines on PAS (2018): Prenatal diagnosis, conservative & non-conservative management.
  • IS-AIP (AJOG 2019): Evidence-based guidelines for abnormally invasive placenta; plus SMFM Special Report on PAS Centres of Excellence (AJOG 2021).


Compiled By:

Dr. Fahmida Islam Chowdhury


Contributors

  1. Prof Fawzia Hossain
  2. Prof Firoza Begum
  3. Prof Salma Rouf
  4. Dr Hasina Begum
  5. Dr Maniza
  6. Dr Farzana Deeba
  7. Dr Sanjana Ahmed
  8. Dr Shaharin Chowdhury
  9. Dr Sumona Parvin
  10. Dr Tasrina Akter
  11. Dr Shamrin Sultana
  12. Dr Md. Sajid Bin Ashraf Sami
  13. Dr Kamrun Nahar
  14. Dr Nurun Nahar
  15. Dr Nadia Ferdouse Ria