[Macroscopic description of placental vascular anastomoses after dye injection for the comprehension of monochorionic pregnancy complications].

Objectives: The aim of the study is to compare placental monochorionic angioarchitecture complicated with twin-oligohydramnios-polyhydramnios sequence (TOPS), twin anemia polycythemia sequence (TAPS), twin reversed arterial perfusion (TRAP) and selective intra uterine growth restriction (sIUGR) to normal uneventful monochorionic placenta.

Methods: Between December 2012 and December 2015, monochorionic placenta has been studied at the multiple pregnancy care center of the Femme-Mère-Enfant Hospital in Lyon. Umbilical chords were catheterized and dye injected for macroscopic analysis of angioarchitecture at the anatomopathology department. Placentas treated with laser foetoscopic surgery were excluded.

Results: A total of 126 placentas were injected in the post-partum period. In total, 95% (119/126) of the placentas presented arteriovenous anastomoses (AVA). Median number of AVA was 7. The prevalence of at least one velamentous cord insertion was higher in TOPS and selective intrauterine growth restrictions P<0.01 and P<0.01 respectively, compared to uneventful pregnancies. Arterio-arterial anastomoses (AAA) were present in 82.7% (77/93) of uneventful placentas versus 33.3% of TOPS (P<0.01) and 28.5% of TAPS (P<0.01). The prevalence of veno-venous anastomoses was significantly higher in TOPS (P<0.01). All TAPS placentas showed marginal arteriovenous anastomoses. In TRAP placenta, the acardiac twin had no specific vascular territory.

Conclusion: The study confirms literature findings on prevalence of vascular anastomoses in monochorial placentas, suggesting the protective role of AAA in TOPS and TAPS. The role of VVA is yet hard to determinate. Macroscopic observations of monochorionic placentas are valuable and essential keys for understanding, managing and treating anastomotic syndromes.