Objective: Discordance in nuchal translucency measurements in monochorionic diamniotic twin pregnancies was assessed as predictor of Twin-to-Twin Transfusion Syndrome. Study Design: A total of 61 monochorionic diamniotic twins were enrolled. Nuchal translucency (NT) and crown-rump-length (CRL) discordance was calculated as the percentage of delta NT and CRL (absolute difference NT/CRL fetus 1 and fetus 2) of the largest measurement, and correlated with subsequent development of Twin-to-Twin Transfusion Syndrome. Results: Twin-to-Twin Transfusion Syndrome developed in 14/61 (23%) of cases. A NT discordance of 20% or more best predicted Twin-to-Twin Transfusion Syndrome development, with a sensitivity of 64% and a specificity of 78%. We found a positive predictive value of 50% and negative predicted value of 86% for Twin-to-Twin Transfusion Syndrome development if NT discordance was 20% or more. Conclusion:NT discordance of more than 20% in monochorionic diamniotic twins is associated with an increased risk for subsequent development of Twin-to-Twin Transfusion Syndrome, and with earlier presentation of symptoms.