Twin Anemia-Polycythemia Sequence (TAPS)

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] MCDA + MCA-PSV twin discordance + stage
   MCDA + MCA-PSV twin discordance + stage? (TAPS = chronic unidirectional transfusion through tiny (<1 mm) AV anastomoses in monochorionic twins → donor anemia, recipient polycythemia, but no amniotic fluid discordance (distinguishing it from TTTS). Spontaneous ~3–5%, post-laser ~2–13%. Diagnosis: donor MCA-PSV >1.5 MoM, recipient <1.0 MoM; newer delta MCA-PSV >0.5 MoM (more sensitive). Screen MCA-PSV in MCDA from ~20 weeks (especially after TTTS laser).)
   • Stage 1: donor >1.5 / recipient <1.0 MoM (or delta >0.5), no involvement → Stage 1–2 · expectant close monitoring
   • Stage 2: donor >1.7 / recipient <0.8 MoM, no involvement → Stage 1–2 · expectant close monitoring
   • Stage 3 + donor cardiac involvement (critical Doppler) / stage 4 donor hydrops / stage 5 demise → Stage 3–5 → laser/transfusion
2. [End] Stage 1–2 · expectant close monitoring
   TAPS stage 1–2 (no fetal involvement): expectant + close MCA-PSV/Doppler monitoring (may be non-progressive or progress); decide by gestation and progression — stable cases followed to an appropriate gestation for delivery; far from term and progressing, consider fetoscopic laser/intrauterine transfusion.
3. [End] Stage 3–5 → laser/transfusion
   TAPS stage 3–5 (donor cardiac involvement/hydrops/demise): fetoscopic laser coagulation of the anastomoses is definitive; donor intrauterine transfusion ± recipient partial exchange as a bridge; near term → deliver; assess survivors for brain injury; multidisciplinary.

Source guidelines & references

• TAPS diagnosis and staging (Delphi consensus UOG 2020; delta MCA-PSV)

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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