Antenatal detection of arterio-arterial anastomoses by Doppler placental assessment in monochorionic twin pregnancies.

OBJECTIVES: To evaluate the reproducibility of Doppler antenatal detection of arterio-arterial anastomoses (AAA) in monochorionic (MC) twin pregnancies. METHODS: Between October 2002 and February 2004, 21 MC diamniotic twin pregnancies and one dichorionic triamniotic triplet seen at the Twin Clinic at the University of Brescia were recruited. After routine ultrasonographic assessment, AAA were searched using Color or Power and spectral Doppler. The presence of AAA was confirmed postnatally by placental injection studies. RESULTS: Data of 19 patients were available for the analysis. AAA were detected in 12 cases (63%) antenatally and in 16 (84.2%) at injection study. Sensitivity and specificity of Doppler for detecting AAA were 75 and 100%, respectively. Detection rates increased at advanced gestations and with anterior/fundal placentae. The incidence of twin-twin transfusion syndrome was higher in the group with no AAA detected in vivo compared to the group with AAA found with Doppler (28.5 vs. 16.6%), but the difference was not statistically significant (p = 0.5). CONCLUSION: This study confirmed the feasibility of AAA Doppler detection in vivo in MC pregnancies.