[Significance of twin to twin transfusion syndrome in the prognosis of twin pregnancies and its prenatal diagnosis by ultrasonography].

The reason why TTS worsen the prognosis of twin pregnancies was discussed with reference to case results for perinatal death, and antenatal diagnostic criteria for TTS by ultrasonography was established. Of 12 perinatal deaths in 71 twin pregnancies, eight fetuses were affected with TTS (1 acardia, 4 donors, 3 recipients). Perinatal mortality rate (39.3%), rate of preterm lobar (62.2%), rate of polyhydramnion (50.0%), mean amniotic fluid volume (3.310 ml) and cord cross section area ratio (2.38) in monochorionic discordant twins were higher than in the other three groups (monochorionic concordant twins, dichorionic discordant twins and dichorionic concordant twins). Eight fetuses among 12 monochorionic discordant twins were affected with TTS. All twins which showed a single GS in early pregnancy were monochorionic twins. Therefore TTS was considered to have a poorer prognosis than usually reported for all TTS, and to find monochorionic discordant twins with a high cord cross section area ratio must be the key in the screening of TTS. Antenatal diagnosis of TTS by ultrasonography is summarized as follows: 1) A single GS in early pregnancy. 2) Estimated body weight difference between the twins/estimated body weight of the larger twins greater than or equal to 0.2. 3) Cord cross sectional area ratio greater than or equal to 2.0.