Incidental Septostomy after Laser Surgery for Twin-Twin Transfusion Syndrome: Perinatal Outcomes and Antenatal Management.

INTRODUCTION: Incidental septostomy, or inadvertent perforation of the twins' dividing membranes, can create a functional monoamniotic twin pregnancy. Our aim was to describe the perinatal outcomes and antenatal management of patients with incidental septostomy after laser surgery for twin-twin transfusion syndrome (TTTS). MATERIALS AND METHODS: Monochorionic diamniotic multiple gestations with a gestational age (GA) between 16 and 26 weeks that underwent laser surgery from March 2006 to December 2015 were studied retrospectively. Perinatal outcomes were compared for patients with and without an incidental septostomy. A subgroup analysis was performed to evaluate antenatal management. RESULTS: Of 532 TTTS patients who underwent laser surgery, incidental septostomy occurred in 34 (6.4%). Compared to all others, patients with a septostomy had an earlier median (range) GA at delivery (30.8 [18.6-37.9] vs. 34.0 [19.3-40.4] weeks, p < 0.0001) and lower 30-day survival of at least one twin (85.3 vs. 94.6%, p = 0.0452). We found no evidence that inpatient fetal surveillance was protective. DISCUSSION: Incidental septostomy in TTTS patients treated via laser surgery appeared to be associated with lower GA at delivery and perinatal survival of at least one twin. Further study is required to determine the optimal antenatal surveillance strategy.