Aim To evaluate the effects of gestation (before or after 20 weeks (weeks)) at which fetoscopic laser ablation (FLA) is performed on outcome for severe TTTS.

Methods A cohort of consecutive monochorionic twin (MC) pregnancies complicated by severe TTTS (≤26 wks) treated by FLA (October 2004–June 2010).

Results Over the 6 year time period 199 sets of MC twins were managed with FLA; 93 cases were performed prior to 20 completed weeks gestation and 106 after 20 weeks. Prior to 20 weeks 2% were Quintero stage II disease, 79% stage III and 19% stage IV. For FLA after 20 weeks the distribution was 9%, 78% and 13% respectively. There was no significant difference in the stage distribution p=0.05. Survival of ≤1 baby to 28 days was 81% at <20 weeks and 89% at >20 weeks (p=0.65). There was no significant difference in outcomes between the two cohorts. However, the gestational age (GA) at delivery was later in the cohort where FLA was performed after 20 weeks. Multivariate logistic regression analysis revealed that GA at delivery was the only significant factor affecting survival ≤1 baby to 28 days in the group > 20 weeks (OR 1.25 95% CI 1.06 to 1.48 p=0.08). For perinatal mortality a later GA at delivery (OR 0.97 95% CI 0.95 to 0.99 p=0.008) and an experienced operator decreased perinatal mortality (OR 0.17 95% CI 0.04 to 0.83 p=0.03).

Conclusion These data indicate that if FLA is performed <20 weeks then an experienced operator is required and that similar outcomes can be achieved.