Preliminary experience with microwave ablation for selective feticide in monochorionic twin pregnancies

Microwave ablation (MWA) is an alternative technique to radiofrequency ablation and laser ablation in the treatment of some solid tumors. In contrast to radiofrequency and laser ablation, we are not aware of previous experiences with MWA in fetal procedures, and report here our preliminary experience. Two cases of monochorionic–diamniotic twins, discordant for fetal abnormalities, underwent selective feticide by MWA between November 2011 and March 2012. Both patients were informed about the nature of the treatment and possible alternatives and gave their written informed consent. MWA was performed using a 2.45-MHz generator (AMICA-GEN, HS Hospital Service, Aprilia, Italy) delivering energy through a 16-gauge internally cooled coaxial antenna. All the procedures were performed percutaneously under ultrasound guidance. Conscious sedation (delorazepam, 5 mg intravenously) and local anesthetic (10 mL of 2% lidocaine) were administered. The antenna was centered in the abdomen of the abnormal fetus close to the insertion of the umbilical cord (Figure 1a). A single microwave energy application was delivered at 50 W net power at the applicator end for 3 min. In both cases, MWA was technically easy, and ultrasound evidence of tissue coagulation was seen immediately after the beginning of energy delivery (Figure 1b). In the first case, one of the twins had a complex cardiac abnormality (dextrocardia, tricuspid atresia, ventricular septal defect, pulmonary stenosis) complicated by hydrops; cervical length was 22 mm. MWA was performed at 17 + 3 weeks’ gestation. There was premature rupture of membranes of the terminated twin 4 days later, and the entire pregnancy miscarried after 7 days. In the second case, one of the twins had anencephaly; cervical length was 40 mm. MWA was performed at 16 + 2 weeks. The pregnancy carried on uneventfully, and a healthy female infant was delivered vaginally at 39 weeks’ gestation. MWA has many potential advantages over radiofrequency and laser ablation: there is immediate evidence of tissue coagulation on ultrasound; the technique is less dependent on tissue properties, as microwave Figure 1 Ultrasound images showing microwave ablation in Case 2. (a) Antenna is centered in abdomen of abnormal fetus close to insertion of umbilical cord. (b) Two min after start of energy delivery, evidence of tissue coagulation can be seen.