Introduction:
Twin-to-twin transfusion syndrome (TTTS) is associated with increased risk for fetal or neonatal death in one or both twins as well as with increased risk for long term adverse neurological outcomes.1-6 One of the most frequent approaches to evaluate TTTS severity and progression is the Quintero classification system, which is based on sonographic and Doppler findings in the donor and recipient twins.7;8 This TTTS staging system is widely used because of its simplicity. However, there are conflicting reports on whether or not the Quintero staging system is predictive of fetal or neonatal survival.7-11 Fetal echocardiography has been used to further stratify TTTS severity and to determine the adequate timing for laser photocoagulation of placental anastomoses.12-15 However, the largest series for the management of TTTS published to date did not include fetal echocardiography information.7;16;17 This is presumably because its role in the evaluation of TTTS severity remains controversial,12-15 and because comprehensive fetal echocardiography may not always be available prior to laser surgery.
We previously reported that small intertwin differences in impedance to blood flow in the umbilical arteries (UA) among TTTS cases with Quintero Stage I or II is associated with infant survival independent from gestational age at delivery, Quintero stage, selective fetal growth restriction (sFGR) and other confounding variables.9This study is designed to determine the role of intertwin differences in the UA pulsatility index (DUAPI) in predicting infant survival among TTTS cases with Quintero stages III or IV.