Changes in umbilical venous volume flow after fetoscopic laser occlusion of placental vascular anastomoses in twin-to-twin transfusion syndrome

Objective To examine effects of fetoscopic laser occlusion of placental vascular anastomoses on umbilical venous volume flow in twin-to-twin transfusion syndrome. Study Design Absolute umbilical venous volume flow, measured preoperatively and 48 hours after fetoscopic laser occlusion was related to Doppler studies, bladder filling in donors, and anastomoses. Results Among 45 patients, recipients had decreased ductus venosus pulsatility index (ductus venosus-pulsatility index for veins, 1.16 vs 1.01; P < .001) and unchanged umbilical venous volume flow after fetoscopic laser occlusion (74.7 vs 74.5 mL; P = .407). Donors had decreased umbilical artery pulsatility (1.34 vs 1.11; P = .008), increased ductus venous-pulsatility index for veins (0.75 vs 0.91; P < .014), and significantly increased umbilical venous volume flow per kilogram by 52.3% (136.6 vs 208.0 mL/Kg/min; P < .001). Donor bladder filling occured at higher umbilical venous volume flow per kilogram (142.7 vs 221.4 mL/Kg/min; P < .012). Increase in umbilical venous volume flow per kilogram correlated with the net difference in arteriovenous anastomoses (Pearson r = 0.403, P = .006). Conclusion Fetoscopic laser occlusion in twin-to-twin transfusion syndrome corrects intertwin differences in umbilical venous volume flow by predominant effects in the donor. Reappearance of donor bladder filling correlates with correction of volume flow.