Summary

Summary of Twin–Twin Transfusion Syndrome

Evaluation of the incidence of TTTS is limited by the continuum of mild to severe disease and by the assessment in select populations, including referral centers and population-based studies. By current diagnostic criteria, less than 2% of twins or higher multiple births born >20 weeks’ gestation may develop TTTS. 

This incidence is likely to change with increasing rates of multiple births worldwide. Predicting TTTS in early pregnancy may be more valuable than the diagnosis of clinically overt disease. In addition to its prognostic value, 

Doppler ultrasound studies may play a bigger role in diagnosing TTTS in the future. The true incidence of TTTS may fall somewhere in between the percent of histopathologically abnormal monochorionic placentas and the yet immeasurable subtle manifestations of the syndrome.