Monochorionic twins share a single placenta with intertwin vascular anastomoses, allowing the transfer of blood from one fetus to the other and vice versa. These anastomoses are the essential anatomical substrate for the development of several complications, including twin-twin transfusion syndrome (TTTS) and twin anemia-polycythemia sequence (TAPS). TTTS and TAPS are both chronic forms of fetofetal transfusion. TTTS is characterized by the twin oligopolyhydramnios sequence, whereas TAPS is characterized by large intertwin hemoglobin differences in the absence of amniotic fluid discordances. TAPS may occur spontaneously in up to 5% of monochorionic twins and may also develop after incomplete laser treatment in TTTS cases. This review focuses on the pathogenesis, incidence, diagnostic criteria, management options and outcome in TAPS. In addition, we propose a classification system for antenatal and postnatal TAPS.
Objective To evaluate the diagnostic accuracy of middle cerebral artery peak systolic velocity (MCA-PSV) Doppler measurements in prediction of hemoglobin levels in twin anemia-polycythemia sequence (TAPS).
Methods
Fetal growth restriction in singletons has been shown to enhance fetal lung maturation and reduce the risk of respiratory distress syndrome due to increased endogenous steroid production. However, data on lung maturation in growth-discordant monochorionic (thus, identical) twins are lacking. Our objective was to compare the risk of severe neonatal morbidity between the larger and the smaller twin in monochorionic twins with birth weight discordance (BWD). We included in the study all consecutive monochorionic diamniotic pregnancies with severe BWD (≥25%) and two live-born twins delivered at our center (n = 47 twin pairs). We compared the incidence of neonatal morbidity, particularly respiratory distress syndrome (RDS), and cerebral lesions between the larger and the smaller co-twin. The incidence of severe neonatal morbidity in the larger and smaller twin was 38% (18/47) and 19% (9/47), respectively (odds ratio (OR) 2.66, 95% confidence interval (CI) 0.94-7.44) and was due primarily to the higher incidence of RDS, 32% (15/47) and 6% (3/47), respectively (OR 6.88, 95% CI 1.66-32.83). In conclusion, this study shows that the larger twin in monochorionic twin pairs with BWD is at increased risk of severe neonatal morbidity, particularly RDS, compared to the smaller twin.
FPV values based on Ht values are less reliable than those based on RCV and HbF findings. When, for practical reasons, Ht values have to be used, we propose an adapted equation for the calculation of the necessary volume of donor blood: V(donor) = FPV(HbF) * (Ht(final) - Ht(initial) / (Ht(donor) - 0.70 * Ht(final)).
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