Residual anastomoses in twin-to-twin transfusion syndrome treated with selective fetoscopic laser surgery: localization, size, and consequences.

Objective: To study the localization and size of residual anastomoses in twin-to-twin transfusion syndrome treated with fetoscopic laser surgery and correlate the findings with outcome.
Study Design: Placental injection in twin-to-twin transfusion syndrome placentas treated with laser was performed by using colored dye.
Results: A total of 77 twin-to-twin transfusion syndrome placentas were included in the study. Residual anastomoses (n = 48) were found in 32% (25/77) of lasered placentas. Most residual anastomoses were localized near the margin of the placenta. The majority of residual anastomoses (67%; 32/48) were very small (diameter, < 1 mm). Eleven of the 25 cases (44%) in the residual anastomoses group developed twin anemia-polycythemia sequence.
Conclusion: Most residual anastomoses in twin-to-twin transfusion syndrome placentas treated with laser are very small and localized near the placental margin. Almost half of cases with residual anastomoses developed twin anemia-polycythemia sequence after laser surgery.