Optimisation of highly selective fetoscopic laser by indicated septostomy for twin-twin transfusion syndrome

Introduction Fetoscopic laser ablation (FLAP) is established as the first line management in severe twin-twin transfusion syndrome (TTTS). FLAP in combination with elective septostomy to equilibriate liquor has been associated with poorer outcome compared to FLAP alone, due to risks associated with iatrogenic monoamnionicity. However, in cases where the recipient cord insertion lies in close proximity to the intertwin membrane, ablation of vessels too close to the cord has high risk of death in utero. We report our results of indicated septostomy in this scenario with visualisation of both donor and recipient placental territory in order to optimise fetoscopic laser ablation of intertwin anastomoses. Methods Subjects with TTTS and cord insertion adjacent to the intertwin membrane or a suggestion of anastomoses crossing the membrane underwent selective septostomy and a therefore more targeted FLAP. Results Six subjects with severe TTTS underwent FLAP with septostomy at a mean gestation of 23.2 weeks. Additional ablation within the donor sac was performed in 4/6 cases. In the remaining 2/6 cases, there were no anastomoses in one and a large anastomosis in the second, which was not ablated due to high risk of vessel rupture. In this series, perinatal survival was 100%, mean gestation at delivery was 31.4±1.4 weeks and mean birthweight was 1618 ±499 g. All subjects underwent delivery by Caesarean section. Conclusion Selective septostomy when the cord insertion is close to the intertwin membrane may have a role in facilitating placental mapping and targeted FLAP to intertwin anastomoses to improve outcomes of such pregnancies.