Background: Monochorionic diamniotic (MCDA) twins are at significantly increased risk of perinatal morbidity and mortality due to shared placentation and the presence of inter-twin placental vascular anastomoses. Aim of the work: The main aim of this study was to validate first trimester ultrasound screening for twin-to-twin transfusion syndrome (TTTS) and selective intrauterine growth restriction (sIUGR) in monochorionic twin pregnancies using the triad of nuchal translucency (NT), cord insertion site and inter-twin discordance in fetal size. Summary: We have demonstrated that NT and CRL were significantly higher in TTTS group than sIUGR group. And difference in NT, CRL and cord insertion site was identified as predictive markers for sIUGR and TTTS.