Antenatal detection of arteriovenous anastomoses in monochorionic twin pregnancy

OBJECTIVES: To revalidate the detection technique for arteriovenous anastomoses in an unselected group of monochorionic twins, and to make recommendations about its applicability for more widespread use. METHODS: Women with monochorionic diamniotic (MCDA) twins were recruited and underwent placental mapping by color Doppler ultrasound. Images of placental maps showing the location and type of anastomoses were saved as digital video clips. After delivery, dye injection study of all the placentas was performed to delineate the site and type of anastomoses. A digital photograph of each injection study was taken and saved. The antenatal ultrasound images and postnatal dye injection studies were compared. RESULTS: 18 sets MCDA twins were evaluated. In 3 cases there was evidence of twin-to-twin transfusion syndrome. Dye injection of 18 placentas revealed 21 arterio-arterial anastomoses (AAA), 21 arteriovenous anastomoses (AVA) and 4 veno-venous anastomoses (VVA). Of these, 10 (48%) AAAs and 5 (24%) AVAs were detected antenatally by color Doppler. In all cases, where an AVA was detected, the placenta was located anteriorly. CONCLUSION: Antenatal detection of AVA was feasible when the placenta was located anteriorly, but proved difficult in posteriorly situated placentas.