| Traditional staging system (primarily based on MCA-PSV thresholds): |
- Stage 1 – Donor twin MCA-PSV >1.5 MoM, recipient twin <1.0 MoM, without other signs of fetal compromise
- Stage 2 – Donor MCA-PSV >1.7 MoM, recipient twin <0.8 MoM, without other signs of fetal compromise
- Stage 3 – Stage 1 or 2 plus donor cardiac compromise by any of the following:
- UA:
- Absent or reversed end-diastolic velocity
- Pulsatile flow
- DV:
- Increased pulsatility index
- Reversed flow
- Stage 4 – Stage 1 or 2 plus donor hydrops
- Stage 5 – Demise of one or both fetuses preceded by TAPS
|
| Emerging staging system (primarily based on intertwin MCA-PSV discordance): |
- Stage 1 – Delta MCA-PSV >0.5 MoM; without signs of fetal compromise
- Stage 2 – Delta MCA-PSV >0.7 MoM; without signs of fetal compromise
- Stage 3 – Stage 1 or 2 delta MCA-PSV findings plus cardiac compromise of the donor or recipient fetus based on abnormal Doppler flow studies in the UA or DV or hydrops fetalis (predominantly in the donor fetus)
- Stage 4 – Demise of one or both fetuses preceded by TAPS
|
| Postnatal staging system (based on the hemoglobin difference between twins): |
- Stage 1 – >8 g/dL
- Stage 2 – >11 g/dL
- Stage 3 – >14 g/dL
- Stage 4 – >17 g/dL
- Stage 5 – >20 g/dL
|
