Radiofrequency ablation (RFA)
All patients were admitted to the hospital in a day before the day of the procedure of RFA after undergoing a comprehensive assessment before fetal therapy procedure. All procedures were conducted by the combination of one fetology specialist and one interventional ultrasound specialist in the intrauterine therapeutic room of Medical Genetics Center.
All patients were treated using the RF-1500 RFA system (MedSphere international (Shanghai) CO., Ltd, China). According to RFA protocol9, local anesthesia was conducted at the planned puncture site on the maternal abdomen (2% lidocaine hydrochloride administered subcutaneously).Under continuous sonographic guidance, a 15cm or 20cm 17-gauge RFA electrode needle was inserted form fetal abdomen or back to adjacent to the area of the umbilical cord insertion, after confirmation of the location, the umbrella Electrode were deployed.RFA energy was applied start from 20 watts, increasing 10W per minute, until the impedance exceeds the critical value, when the host stop active output. If the impedance don’t exceed, maintain ablation 2-3min after reaching target temperature of 100 ℃. The procedure was repeated for an additional one or two cycles using the same heating algorithm, until cessation of cord blood flow was confirmed using color and power Doppler velocimetry.
Follow-up was organized locally through multiple contact methods, such as telephone and some internet contact. All surviving fetuses underwent a head MRI after 28 weeks of gestation to assess fetal neurological development and to determine if there was a brain injury. Pregnancy and neonatal outcome data were obtained from the clinical notes or from referring physicians, and missing data were collected by telephone interview with the patients.