P346: Prenatal detection of arterio-arterial anastomoses in cases of twin-to-twin transfusion syndrome

To detect the presence of arterio-arterial anastomoses (A-A A) in monochorionic twins suffering from twin-to-twin transfusion syndrome. We analyzed 11 monochorionic twin pregnancies and 2 monochorionic triplet pregnancies. Arterio-arterial anastomoses were identified by color and pulse wave Doppler facilities presenting typical bidirectional pattern of blood flow. The presence of vascular shunts was confirmed postnatally by injection study. The diagnosis of TTTS was made on the basis of following criteria: poly/oligohydramion, growth discordance > 20%, abnormal Doppler studies. We were able to visualize at least one A-A A in 46% of TTTS cases. The sensitivity of prenatal detection of A-A A was 86% with specificity of 100%. Prenatally, we were able to detect no more than one anastomosis in each case. Postnatally confirmed anastomoses ranged from 1 to 7. The majority of them were very thin and narrow. In the group with prenatally confirmed A-A A (n = 6; 12 fetuses) there were 7 survivors (58%). In the group without anastomoses (n = 7; 14 fetuses) there were 5 survivors (36%). Mean gestational age in both groups was 31 weeks. Mean growth discordance in the first group was 42%, and in the second 26%. A-A anastomoses may be identified by Doppler studies. Undetectable anastomoses are due to their lack or the absence of their paucity. In these pregnancies worse fetal outcome was noticed.