Pre-operative Predictors of Survival in Twin-Twin Transfusion Syndrome Undergoing Fetoscopic Laser Treatment

Introduction Limited data exist regarding the effect of pre-operative risk factors on fetal survival for patients undergoing fetoscopic laser photocoagulation (FLP) for twin-twin transfusion syndrome (TTTS). The primary objective of this study was to determine the pre-operative variables predictive of single and dual fetal survival at birth for subjects treated with laser for TTTS. The secondary objective was to determine the combined effect of multiple risk factors on single and dual fetal survival at birth. Methods This was a prospective cohort study of TTTS pregnancies treated with FLP between 2001-2023. Cases were identified through the monochorionic twin pregnancy registry of the North American Fetal Therapy Network. Several pre-operative risk factors were evaluated including maternal BMI, gestational age at laser, fetal growth restriction (FGR), cervical length, placental location, and TTTS stage. Higher order multiples, fetal anomalies, karyotypic abnormalities, and cases with missing data were excluded. Risk factors influencing survival were assessed with uni- and multi-variate regression analyses. The predicted probability of single/dual survival based on these risk factors were assessed with multiple logistic regression analysis. Results Of 2,728 FLP cases, 1,066 met inclusion criteria. Dual survival is reduced in stage 3 & 4 disease compared to stage 1&2 (OR 0.75: 0.58,0.98; p=0.032) with lowest survival in all stages occurring with FGR. An anterior placenta (aOR 0.58: 0.37,0.91; p=0.017) and FGR<10th percentile (aOR 0.57: 0.35,0.92; p=0.02) were independent predictors of reduced survival. With regression modeling, sequential addition of any pre-operative risk factor progressively reduces survival of at least one or both twins. Conclusions In this large registry, anterior placental location and FGR were most predictive of reduced survival for both twins. As the number of pre-operative risk factors increase for a given TTTS case, there is a progressive reduction in survival probability and these reported probability rates may be useful in counseling patients.