EP07.10: Are the current antenatal diagnostic criteria for twin anemia polycythemia sequence adequate?

Abstract

We describe two cases of spontaneous twin anemia polycythemia sequence (TAPS). In Case 1, TAPS was suspected at 21 weeks because of discrepancy in placental echogenicity in two portions of the placenta. However, the antenatal (AN) diagnostic criteria for TAPS were not met. MCAPSV of the recipient was low but that of the donor was never >1.5 MoM. The diagnosis was confirmed after delivery. In Case 2, MCAPSV of the twins at 30 weeks were 0.89 and 1.42 MoM respectively. The placental echogenicity was normal. Routine monitoring two weeks later found single intrauterine death (IUD). MCAPSV of the surviving fetus dropped to 0.7 MoM. The placental portion of the dead fetus was thick and echogenic while that of the surviving fetus was thin and hypoechoic. There was no liquor discrepancy. The findings were suggestive of TAPS with IUD of the donor. The efficacy of AN diagnosis of TAPS by Slaghekke's proposed criteria of MCAPSV >1.5 MoM in the donor and <1.0 MoM in the recipient has not been studied. Cases fulfilling these diagnostic criteria must have an intertwin MCAPSV difference of >0.5 MoM. In both of our cases, the MCAPSV of the donors were below 1.5 MoM. But the intertwin MCAPSV difference was consistently >0.5 MoM after 21 weeks in Case 1 and in Case 2, the difference was also >0.5 (0.53) MoM at 30 weeks. If an intertwin MCAPSV difference of >0.5 MoM is used for diagnosis, TAPS could be picked up in Case 2 so that intensive monitoring and early intervention would prevent IUD of the donor. In Case 1, although TAPS was diagnosed by discrepancy in placental echogenicity, this finding may not appear before serious complications occur as in Case 2. Our cases illustrated that an intertwin MCAPSV difference of >0.5 MoM may detect TAPS better than the absolute MCAPSV cutoffs. To avoid inclusion of cases with anemia or polycythemia alone, MCAPSV cutoffs are still needed but the current donor cutoff may need to be lowered. Further studies are required for confirmation.