Correction of fetal umbilical vein flow imbalance following laser surgery for twin–twin transfusion syndrome

ABSTRACT Objectives Twin–twin transfusion syndrome (TTTS) is characterized by unequal hemodynamics between the twins. We aimed to assess preoperatively the difference in umbilical vein flow (UVF) between the recipient and donor monochorionic diamniotic twins and evaluate the change in UVF following laser surgery in both twins. Methods This was a retrospective cohort study of differences in UVF that occurred following laser surgical treatment of TTTS. Sonographic assessment of the umbilical vein before and 24 h after fetoscopic laser surgery for TTTS was performed. Umbilical vein diameter and time‐averaged maximum velocity were measured, and UVF per kg (UVF/kg) was converted into a Z‐score by a calculator created using gestational age as an independent variable. Z‐score values were converted into centiles, which were evaluated statistically. Median differences in UVF/kg centile values were adjusted for TTTS stage and presence of arterioarterial anastomoses. Results The study population consisted of 363 TTTS patients. The adjusted preoperative median difference in UVF/kg centile between the recipient vs donor twin was 17.9% (−17.1% to 57.6%), P