Hematological characteristics in neonates with twin anemia-polycythemia sequence (TAPS)

Objective To evaluate the neonatal hematological features of monochorionic twins with twin anemia–polycythemia sequence (TAPS) and to determine the additional diagnostic value of reticulocyte count measurement. Methods A cohort of consecutive monochorionic twins with TAPS (n = 19) was included in the study and each twin pair was compared with two monochorionic twin pairs (n = 38) unaffected by TAPS or twin–twin transfusion syndrome (TTTS), matched for gestational age at birth. We measured full blood counts on day 1 and determined the incidence of anemia, polycythemia, reticulocytosis and thrombocytopenia. Results Median inter‐twin hemoglobin (Hb) difference in monochorionic twins with and without TAPS was 13.7 g/dL and 2.4 g/dL, respectively (p < 0.01). Median inter‐twin reticulocyte count ratio in twins with and without TAPS was 3.1 and 1.0, respectively (p < 0.01). Thrombocytopenia (platelet count < 150 × 109/L) occurred more often in the TAPS group than in the control group, 45% (17/38) versus 11% (11/38), respectively (p < 0.01). In the TAPS group, mean platelet count was significantly lower in recipients than in donors, 133 × 109/L versus 218 × 109/L, respectively (p < 0.01). Conclusions TAPS twins have a large inter‐twin Hb difference in combination with a large inter‐twin reticulocyte count ratio. Recipients are more often thrombocytopenic than donors, probably due to polycythemia. Copyright © 2010 John Wiley & Sons, Ltd.