Residual Vascular Communications in Twin-twin Transfusion Syndrome Treated With Sequential Laser Surgery: Frequency and Clinical Implications

Abstract

Unbalanced sharing of blood through vascular communications in the common placenta is thought to be responsible for the development of twin-twin transfusion syndrome (TTTS) in monochorionic diamniotic twins. Fetoscopic laser surgery treats TTTS in utero by ablating placental vascular communications. The resulting separation of the fetal circulatory systems improves perinatal survival and neurological outcome. Several studies have demonstrated that, after laser surgery, residual vascular communications (RVC) may be present in up to one-third of cases, and may be associated with persistent TTTS or twin anemia-polycythemia sequence (TAPS) and other adverse perinatal outcomes. A wide range of RVC rates (from 32% to 75% of cases) have been reported in similar patient populations. This variability in RVC rates has been attributed to the laser technique used and the method of placental evaluation. The primary aim of this study was to determine the frequency of residual RVC in a large series of placentas treated in utero for TTTS using preferential sequential selective laser photocoagulation of communicating vessels. A secondary aim was to investigate potential clinical risk factors associated with RVC and perinatal outcomes of cases complicated by RVC. The study subjects were pregnant women who underwent preferential sequential selective laser photocoagulation of communicating vessels for TTTS from 2006 through 2009 at an academic medical center. After delivery, placentas were submitted for examination and water and/or milk injections were used to assess the patency of vascular communications between the twins. Cases with placental disruption and intrauterine fetal demise were excluded from the analysis. Perinatal outcomes of cases with and without RVC were compared. Over the 3 years of the study, 174 women with TTTS were treated by preferential sequential selective laser photocoagulation of communicating vessels. Of the 174 cases, 133 (76%) resulted in survival of both twins at birth, and 105 (79%) of these submitted an intact placenta for pathological evaluation. Injection studies showed the presence of RVC in 5 of the 105 placentas (4.8%). One of the 5 RVC cases (20%) had neonatal findings consistent with TAPS, whereas none of the no-RVC cases had TAPS. There was one case of persistent TTTS in the no-RVC group. The gestational age, estimated fetal weights, and amniotic fluid volumes in each sac at the time of the procedure were similar in RVC and no-RVC cases. There was a trend toward a longer operative time in RVC cases (63.4 vs. 44.4 min; P = 0.057), but this did not reach statistical significance. Outcomes of RVC and no-RVC cases were also similar: gestational age at delivery = 28.7 ± 6.5 versus 33.4 ± 3.3 weeks (P = 0.178), and donor birth weight = 1429 ± 1369 versus 1653 ± 715 g (P = 0.518). The only differences between the groups were that the no-RVC group had a higher recipient birth weight (1287 ± 1061 vs. 1973 ± 610 g; P = 0.020), and the donor in the RVC cases was more likely to have central or eccentric placental cord insertion (80% vs. 17%; P = 0.006). No histological differences were found between the placentas with and without RVC. These findings show that the frequency of RVC among gestations with dual survivors after preferential sequential selective laser photocoagulation of communicating vessels treatment for TTTS was less than 5%.