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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Placenta accreta spectrum

Obstetrics and gynaecology · UK scope · Sources checked 7 Sept 2026 · Clinical review pending

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Unexpected adherent placenta with major bleeding risk

A placenta that does not separate normally, especially over a uterine scar, may represent accreta spectrum and can bleed catastrophically if forcibly removed.

Action: Stop attempts at placental separation, call the senior obstetric and anaesthetic team, activate haemorrhage support as indicated and obtain immediate specialist surgical advice.

Synopsis

Identify abnormal placental attachment early, arrange specialist surgical planning, and prevent catastrophic bleeding from unplanned placental separation at birth.

  • Placenta accreta spectrum describes abnormal placental attachment associated particularly with implantation in a uterine scar defect.
  • Risk is especially high when placenta praevia overlies a previous caesarean scar; the number and type of prior uterine procedures matter.
  • Expert greyscale ultrasound with colour Doppler is central to assessment; routine MRI is not required when adequate ultrasound expertise is available.
  • NICE recommends expert assessment around 28 weeks and no later than 29 weeks after low placentation is identified in a scarred uterus; earlier suspicion merits earlier specialist referral.
  • The 2026 RCOG key recommendation gives 36+1–37+0 weeks without bleeding or additional preterm-birth risk, but the section 10.2 table differs; agree timing through specialist review of the latest advice.
  • Birth belongs in a specialist centre with a coordinated surgical, anaesthetic, transfusion, critical-care and neonatal plan.
  • Avoid cutting through or attempting to detach a placenta with a high probability of accreta; methotrexate is not recommended when placenta is left in situ.

Key red flags

Previous caesarean birth with an anterior low-lying placenta or praevia requires targeted assessment for placenta accreta spectrum.

Unexpected failure of placental separation, marked uterine surface vascularity or severe bleeding during extraction demands urgent senior surgical support.

Investigation priorities

01
Review of prior uterine surgeryFirst step

Identify scar location and procedures that change the probability of abnormal placental attachment.

Management branches

DetectionEscalate the antenatal probability assessment

Low placentation and uterine scarring or suspicious sonographic signs are identified.

  1. Refer to an experienced ultrasound service and provide the scar history, latest placental location and relevant symptoms.
  2. Arrange assessment by a specialist accreta team when suspicion persists, communicating urgent bleeding or threatened labour directly.
  3. Explain that the imaging predicts operative risk and guide further investigations toward questions that will alter the surgical plan.

Key medicines

Haemorrhage support within the accreta surgical planBlood components and perioperative haemostatic medicines require the specialist obstetric haemorrhage prescription, adjusted to actual loss, laboratory or viscoelastic results and organ function; a fixed universal regimen cannot cover the differing operative approaches.Ensure blood products are physically available, monitor calcium and temperature during transfusion, and coordinate thromboprophylaxis timing with haemostasis and neuraxial anaesthesia.
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Sources and review status4 sources · checked 7 Sept 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 7 Sept 2026; clinical approval remains outstanding.

  • RCOG 2026 Green-top 27a placenta accreta spectrum
  • NICE NG192 caesarean birth and placenta accreta spectrum
  • NICE rationale for specialist accreta assessment
  • RCOG public information about placenta accreta

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom