With selective laser photocoagulation, anastomoses crossing between the twins along the vascular equator are individually coagulated (Ville, 1995). Unfortunately, residual anastomoses remain in up to a third of cases and may lead to TTTS recurrence or to the development of twin-anemia polycythemia sequence (TAPS). The latter is a feto-fetal transfusion characterized by large diferences in hemoglobin concentrations between a pair of monochorionic twins. To address these complications, the Solomon technique was developed. With this, after selective photocoagulation, the laser is used to coagulate the entire vascular equator, from one edge of the placenta to the other (Slaghekke, 2014a). he Solomon technique lowers the proportion of pregnancies with recurrent TTTS and TAPS in multiple trials. Also, placental dye-injection studies confirm a significant reduction in the number of residual anastomoses (Ruano, 2013; Slaghekke, 2014b).
Complications. Families should have reasonable expectations of procedural success and potential complications. Without treatment, the perinatal mortality rate for severe TTTS is 70 to 100 percent. Following laser therapy, the anticipated perinatal mortality rate approximates 30 to 50 percent, with a 5-to 20-percent risk for long-term neurological handicap (Society for Maternal-Fetal Medicine, 2013). Cystic periventricular leukomalacia and grade III to IV interventricular hemorrhage are identiied neonatally in up to 10 percent of laser-treated cases (Lopriore, 2006).
Procedure-related complications include preterm prematurely ruptured membranes in up to 25 percent, placental abruption in 8 percent, vascular laceration in 3 percent, amnionic band syndrome resulting from laser laceration of the membranes in 3 percent, and TAPS in 16 percent with photocoagulation and 3 percent with the Solomon modification (Habli, 2009; Robyr, 2006; Slaghekke, 2014b). Finally, most laser-treated TTTS pregnancies deliver before 34 weeks.
FIGURE 16-5 Fetoscopic photograph of laser photocoagulation for twin-twin transfusion syndrome. A. Vascular anastomoses (arrows) are shown before photocoagulation is performed. B. The ablation sites appear as blanched yellow-white areas (arrows). (Used with permission from Dr. Timothy M. Crombleholme.) he prevalence of congenital diaphragmatic hernia (CDH) is approximately 1 in 3000 to 4000 births, and the overall sur vival rate is 50 to 60 percent. Associated anomalies occur in 40 percent of cases and confer a considerably lower survival rate.
he main causes of mortality among those with isolated CDH are pulmonary hypoplasia and pulmonary hypertension. And, the major risk factor is liver herniation, which complicates at least half of cases and is associated with a 30-percent reduction in the survival rate (vfullassery, 2010, Oluyomi-Obi, 2017).
Because of maternal and fetal risks associated with fetal surgical intervention, eforts have focused on identiying those least likely to survive with postnatal therapy alone. Fetuses with associated anomalies are typically excluded, as are those with out liver herniation. Prediction is further hampered because of improvements in neonatal care for newborns with CDH. These include permissive hypercapnia, "gentle ventilation" to avoid barotrauma, and delayed surgery.