Cesarean Scar Pregnancy (CSP) Ultrasound Diagnosis

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.

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Full pathway

1. [Decision] Gestational sac location and type
   Gestational sac location and residual myometrium — scar pregnancy? Type? (CSP = gestational sac implanted in a prior cesarean scar/niche, can cause hemorrhage/uterine rupture/placenta accreta (PAS). TVUS preferred (semi-filled bladder). Criteria: 1) empty uterine cavity and cervical canal; 2) sac/placenta embedded in the scar (anterior lower segment isthmus at the internal os level); 3) sac filling the scar niche; 4) thin myometrium between sac and bladder (1–3 mm) or absent; 5) rich trophoblastic Doppler flow (high velocity, low resistance).)
   • Type 2 exophytic (deeply embedded, growing toward bladder/serosa, myometrium absent) → Type 2 exophytic · urgent · no curettage
   • Type 1 endophytic (growing toward cavity/isthmus, reasonable residual myometrium) → Type 1 endophytic · early specialist management
   • Not a scar pregnancy (normal intrauterine/low-lying/cervical pregnancy, etc.) → Not CSP · by the relevant type
2. [End] Not CSP · by the relevant type
   Does not meet CSP criteria (normal intrauterine or low-lying pregnancy, cervical pregnancy, etc.): manage by the relevant type; the key to distinguishing CSP is the sac-scar/bladder relationship and residual myometrial thickness; MRI helps when uncertain.
3. [End] Type 1 endophytic · early specialist management
   Type 1 (endophytic, growing toward cavity/isthmus, relatively preserved residual myometrium): still a dangerous pregnancy (bleeding/PAS risk); early termination/specialist management (MTX, ultrasound-guided treatment, UAE adjunct), no blind curettage; closely follow myometrial thickness and flow.
4. [End] Type 2 exophytic · urgent · no curettage
   Type 2 (exophytic, deeply embedded in the scar toward bladder/serosa, myometrium absent): high risk of early uterine rupture/hemorrhage; multidisciplinary urgent management (UAE ± lesion excision/local treatment), blind curettage absolutely contraindicated; MRI assesses depth of invasion and the bladder posterior wall relationship.

Source guidelines & references

• SMFM Consult #63 cesarean scar ectopic pregnancy (AJOG 2022) · source ↗
• ISUOG VISUOG cesarean scar pregnancy (Godin/Vial criteria)

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.

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