Placental markers of twin-to-twin transfusion syndrome in diamniotic–monochorionic twins: A morphometric analysis of deep artery-to-vein anastomoses

Demonstration of angioarchitecture of diamniotic–monochorionic twin placentas following vascular injection. A. Representative diamniotic–monochorionic placenta following vascular injection. Color code: Artery left twin: yellow; vein left twin: green; artery right twin: yellow (through AA anastomosis); vein right twin: black. Arteries cross over veins. Arrows indicate AA anastomosis. B. Close-up of (A) showing abundant AV anastomoses from left twin (A, yellow) to right twin (V, black), indicated by white arrow heads. A minuscule right-to-left AV anastomosis is shown by black arrow head (bottom). A and B: Non-TTTS-pregnancy, 30 weeks' gestation, history of premature rupture of membranes. C. Placenta of pregnancy complicated by TTTS. Left twin is donor, right twin is recipient. Color code: Artery left twin: red; vein left twin: yellow; artery right twin: red (through AA anastomosis); vein right twin: green. Velamentous cord insertion and small placental share of left (donor) twin are noted, as well as relative paucity of intertwin anastomoses. Arrows indicate AA anastomosis. D. Close-up of (C) demonstrating several AV anastomoses from right (recipient) twin to left (donor) twin (black arrow heads). C and D: TTTS-pregnancy, 32 weeks' gestation, fetal demise of both twins.

Correlation between net number of AV anastomoses and absolute net cross-sectional area (NCSA) in TTTS and non-TTTS placentas.

Frequency of TTTS in AV-balanced and unbalanced placentas in association with superficial AA and VV anastomoses. *P<0.05; **P<0.02; ***P<0.001 versus same type of AV balance in presence of corresponding superficial anastomoses.