Placenta Accreta Spectrum (PAS) Imaging

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

🎓 Want to practice? Do a case challenge with this pathway → (get a case, choose management step by step, scored).

Full pathway

1. [Decision] High-risk background + ultrasound signs
   High-risk background + ultrasound PAS signs (± MRI)? (PAS = abnormal placental invasion (accreta to the myometrium/increta into the myometrium/percreta through the serosa ± bladder). High-risk: placenta previa + prior cesarean (rises sharply with number: ~3/11/40/61/67% for 1–5 cesareans). TVUS/transabdominal ultrasound is preferred (sensitivity 81–91%/specificity 97% in high-risk).)
   • No high-risk / no ultrasound PAS signs → Low risk · routine follow-up
   • High-risk + ultrasound PAS signs (≥3 signs) or positive MRI → Suspected PAS → PAS center MDT
2. [End] Low risk · routine follow-up
   No high-risk background and no ultrasound PAS signs (intact clear zone, normal myometrium, no lacunae/bridging vessels): low likelihood of PAS; placenta previa cases still follow the previa pathway, alert for antepartum hemorrhage.
3. [End] Suspected PAS → PAS center MDT
   High-risk (previa + prior cesarean) + ultrasound PAS signs (loss of the clear zone, myometrium <1 mm, lacunae, bladder wall interruption, bridging vessels, placental bulge; ≥3 signs is more accurate): suspected PAS → refer to a PAS center MDT; MRI helps assess depth/extent (intraplacental T2-dark bands most sensitive, posterior placenta); planned cesarean hysterectomy, blood ready, elective delivery.

Source guidelines & references

• Placenta accreta spectrum (SMFM; PMC 2023)
• PAS MRI SAR-ESUR joint consensus (RadioGraphics 2022) · source ↗

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

Other pathways