Rapid Change From Spontaneous Twin Anemia Polycythemia Sequence to Twin-to-Twin Transfusion Syndrome.

A new natural course of spontaneous twin anemia polycythemia sequence (TAPS) was clarified. A 29-year-old woman, who conceived monochorionic diamniotic twins, showed elevation of the peak systolic velocity of the middle cerebral artery (MCA-PSV) in one twin at 24+2 weeks. The other twin showed a decrease in MCA-PSV. The amniotic volume did not differ between the twins. We diagnosed them with TAPS. Four days later, maximum vertical pockets were 19 and 97 mm in the donor and recipient, respectively. We diagnosed them with twin-twin transfusion syndrome, Quintero stage 1. Fetoscopic laser photocoagulation was employed, and the post-operative course was uneventful. Emergent cesarean section was conducted at 33+0 weeks because of premature rupture of the membranes. Neither twin showed anemia nor polycythemia. Only one patient with spontaneous TAPS followed by twin-to-twin transfusion syndrome (TTTS) has been reported so far. To our knowledge, this is the first report of a pregnant woman with TAPS developing TTTS within a few days.