(539) Twin-Twin Transfusion Syndrome after Fetoscopic Laser Photocoagulation: Survival Outcomes According to Gestational Age at Delivery

Objective:
To evaluate 30-day neonatal survival across gestational age (GA) at delivery in pregnancies affected by twin-twin transfusion syndrome (TTTS) treated with fetoscopic laser photocoagulation (FLP).

Study Design:
We conducted a retrospective cohort study of TTTS pregnancies that underwent FLP between 2012 and 2024 at a tertiary fetal center. Pregnancies were stratified by GA at delivery: 23–25⁶, 26–27⁶, 28–29⁶, 30–31⁶, 32–33⁶, 34–35⁶, and ≥36 weeks. Outcomes included (i) survival at delivery and (ii) 30-day neonatal survival, limited to liveborn infants. Survival rates were reported per bracket.

Results:

Among 562 pregnancies, dual survival at delivery occurred in 70.5% and single survival in 19.9% (Figure 1). Among liveborn neonates, 30-day survival of at least one neonate improved significantly with advancing gestational age—from 60.5% at 23–25⁶ weeks to ≥98% in all brackets ≥28 weeks. Fetal loss was most pronounced at the earliest gestations, with 39.5% of fetuses lost by delivery in the 23–25⁶ week group. In contrast, nearly all fetuses survived to birth beyond 28 weeks. Dual 30-day survival peaked at 32–33⁶ weeks (85.3%) and declined thereafter. At ≥36 weeks, single survival predominated (64.9%) due to continued gestation in pregnancies with prior single fetal demise (Table 1).

Conclusion:
In TTTS pregnancies treated with FLP, the highest risk of fetal loss occurs at early gestational ages. Among liveborn infants, 30-day survival improves substantially with increasing gestational age, reaching near-universal survival from 28 weeks onward. However, dual survival is highest between 30–33⁶ weeks and declines at ≥36 weeks, likely due to selective continuation of pregnancies after one twin is lost. These findings support the consideration of late-preterm delivery to optimize outcomes in surviving twins.