P12.13: Reproducibility and clinical relevance of 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 twin pregnancies in a centre other than where this method was first systematically applied and to correlate the prenatal identification of AAA with the clinical outcome of these pregnancies. Methods: 21 monochorionic diamniotic twin pregnancies and one dichorionic triamniotic triplet seen at the Twin Clinic at the University of Brescia were recruited prospectively (October 2002–February 2003). 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. Data on the presence of AAA obtained from injection studies were compared with Doppler findings to establish sensitivities and specificities of prenatal Doppler investigation. Clinical outcome of the two groups (with or without AAA detected in utero) were compared. 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 (TTTS) was higher in the group with no AAA detected in vivo compared to the group with AAA found with Doppler (28.6% vs 16.6%), but not statistically significant (P = 0.5). All TTTS cases with an AAA found in utero, regressed spontaneously or after one amnioreduction. All cases with a birthweight discordance > 20% and no signs of TTTS, had an AAA detected with Doppler and showed intermittent absent/reverse diastolic flow in the umbilical artery of the smaller twin. Conclusion: This study confirmed the reproducibility and clinical relevance of AAA Doppler detection in vivo in monochorionic pregnancies.