Ultrasound diagnosis of twin–twin transfusion syndrome

Over the years, the sonographic definition of TTTS has been particularly marred by lack of standardization. Unfortunately, such lack of standardization has resulted in the inclusion of patients without TTTS in treatment series, or even worse, to unnecessary termination of pregnancy in patients without TTTS.

Hence, the need to establish a standard sonographic approach to TTTS cannot be overemphasized. The original ultrasound reports on the diagnosis of TTTS were based on biometric discrepancies (>10 mm of either the biparietal diameter or the transverse diameter of the trunk between the twins) in addition to polyhydramnios of the larger twin.


Furthermore, Brennan et al suggested that the presence of same sex, disparity in size or in the number of vessels in the umbilical cords, single placenta with different echogenicity of the cotyledons supplying the two cords, and evidence of hydrops in either twin or congestive heart failure in the recipient twin be added to the criteria.7 Doppler studies were also used in an attempt to define the syndrome. With the introduction of the sonographic staging system,8 it is now easy to understand the conflicting findings of the original reports that used Doppler to define the disease, and the actual role that Doppler assessment plays in the assessment of patients with TTTS.