Clinical and placental characteristics in four new cases of twin anemia-polycythemia sequence.

We report and analyze four new cases of spontaneous twin anemia-polycythemia sequence (TAPS) and discuss antenatal management by fetoscopic laser coagulation for this uncommon form of chronic intertwin transfusion. The clinical course and placental characteristics of four pairs of monochorionic-diamniotic (MCDA) twins with spontaneous TAPS, of which one was treated with fetoscopic laser surgery, are described. For the three cases that did not undergo intrauterine intervention, serial Doppler measurement revealed a gradual increase in the middle cerebral artery peak systolic velocity (MCA-PSV) in the donor and a concomitant decrease in the recipient. These twins were born at between 32 and 34 weeks' gestation by Cesarean section. At birth, the donor twins were severely anemic and the recipient twins were polycythemic. Placental injection studies revealed a few small arteriovenous (AV) and venoarterial anastomoses. In the fourth case, because of the high suspicion of TAPS on MCA-PSV data at 24 weeks' gestation, fetoscopic laser coagulation of three small AV anastomoses was successfully performed. No hematological abnormalities were detected at birth. TAPS is a newly described form of chronic twin-to-twin transfusion associated with chronic anemia in the donor and polycythemia in the recipient, without twin oligo-polyhydramnios sequence (TOPS). The monitoring of MCDA pregnancies should include measurement of MCA-PSV in both fetuses even in the absence of intertwin discordance in amniotic fluid volume. Early detection of TAPS could indicate fetoscopic laser coagulation of AV anastomoses.