(100) Phenotype based staging of disease severity in twin-to-twin transfusion syndrome (TTTS)

Objective: Unequally shared placental resources can lead to twin to twin transfusion syndrome (TTTS) and Twin Anemia Polycythemia Sequence (TAPS) due to reciprocal volume or red cell imbalance across anastomoses and selective fetal growth restriction (sFGR) from unequal access to placental territory. These conditions are not mutually exclusive and can co-occur in TTTS at fetoscopic laser surgery (FLS). We sought to understand if categorizing patients by these distinct pathologies might provide insight into survival outcomes after FLS beyond currently utilized staging.

Study Design:

Single center study categorizing 4 phenotypes in FLS patients: TTTS only, TTTS & sFGR (size discordance ≥25%, TTTS & TAPS (middle cerebral artery peak systolic velocity discordance >0.5 multiples of median), and TTTS, sFGR & TAPS. Clinical phenotype, Quintero stage, multiple cardiovascular (CVS) Doppler parameters and placental findings at FLS were related to double survival at 48 hours and birth.

Results: In 382 patients, 208 had isolated TTTS (54.5%), 101 TTTS and sFGR (26.4%), 43 TTTS and TAPS (11.3%) and 30 TTTS, sFGR and TAPS (7.9%; table). Quintero stages III and IV occurred with sFGR (75, 47.2%) or TAPS (13, 54.2%) respectively (p < 0.001). All variables except recipient hydrops and donor absent umbilical artery (UA) end-diastolic velocity were equally distributed across phenotypes. Large diameter placental artery-artery anastomoses were more common in sFGR and small anastomoses in TAPS. 48 hour and birth double survival differed significantly by phenotype, primarily due to the length of post-FLS donor survival in FGR (r²=0.44, p< 0.0001). Donor demise was determined by UA Doppler index which was also inversely correlated with days of donor survival (Pearson -0.24, p< 0.001). Recipient survival was not predictable.

Conclusion: Over 80% of TTTS recipients survive after FLS irrespective of preoperative cardiovascular compromise. While multiple variables reflect TTTS severity, phenotypes correlate with the placental architecture and post laser survival, highlighting sFGR as the primary barrier to double survival.