TAPS in Monochorionic Twin Pregnancy: Diagnostic Criteria by MCA-PSV and Delta MoM
Definition and Essence of TAPS
Twin anemia–polycythemia sequence (TAPS) is a form of chronic inter-twin transfusion imbalance in monochorionic pregnancy. Doppler peak systolic velocity (PSV) measurement in the fetal middle cerebral artery (MCA) is not considered a classification criterion in the Quintero classification for fetofetal transfusion syndrome (TTTS), however it is widely used specifically for TAPS assessment.
Ultrasound Diagnostic Criteria for TAPS
According to ISUOG data, TAPS should be suspected in the following cases:
| Parameter | Threshold Value |
|---|---|
| Donor MCA-PSV | > 1.5 MoM |
| Recipient MCA-PSV | < 1.0 MoM |
| Inter-twin difference (delta) MCA-PSV | > 0.5 MoM |
Thus, diagnosis is established either when elevated PSV in the donor (>1.5 MoM) and reduced PSV in the recipient (<1.0 MoM) occur simultaneously, or when the inter-twin MCA-PSV difference exceeds 0.5 MoM.
Role of Delta MoM
The inter-twin difference (delta) MCA-PSV in MoM is used as an independent diagnostic indicator for TAPS detection. According to literature data, improved TAPS prediction is achieved with the application of delta MCA-PSV; an antenatal classification system based on this parameter has been proposed (Tollenaar LSA et al., 2019). [clarification needed] specific stages of this classification system are not provided in the text fragments.
Frequently asked questions
What MCA-PSV thresholds are used for TAPS diagnosis?
Donor MCA-PSV >1.5 MoM and recipient MCA-PSV <1.0 MoM, or inter-twin difference (delta) MCA-PSV >0.5 MoM.
Is MCA-PSV included in the Quintero classification for TTTS?
No, Doppler MCA-PSV measurement is not considered a Quintero classification criterion for TTTS, but it is frequently used for TAPS assessment.
What does delta MoM mean in the context of TAPS?
It is the inter-twin difference in peak systolic velocity in the middle cerebral artery; a value >0.5 MoM indicates suspicion of TAPS.
Can TAPS be diagnosed based on delta MCA-PSV alone?
Yes, according to ISUOG, a large inter-twin difference (>0.5 MoM) is itself grounds to suspect TAPS, even without the simultaneous presence of both donor and recipient threshold values.