First successful case of non-invasive in-utero treatment of twin reversed arterial perfusion sequence by high-intensity focused ultrasound.

High-intensity focused ultrasound (HIFU) has excellent potential as a non-invasive therapeutic tool in various fields of medicine. We present a case of twin reversed arterial perfusion sequence, in which non-invasive blood flow occlusion in the acardiac fetus was successfully achieved by means of HIFU exposure from outside the maternal abdomen. HIFU was applied to blood vessels of the acardiac fetus at the point at which the umbilical cord entered the body in a series of four procedures at 3-day intervals starting at 13 weeks' gestation, and in a final procedure with higher power at 17 weeks. The HIFU intensity was set at approximately 2300 W/cm(2) for the initial series of procedures and at 4600 W/cm(2) for the final procedure, with exposure periods of 10 s. As color Doppler examination revealed absence of blood flow to the acardiac fetus after the second round of HIFU exposure, we concluded that complete occlusion of target vessels had been achieved. Delivery was by Cesarean section at 37 weeks' gestation. A male neonate (the pump fetus) was born weighing 1903 g with Apgar scores of 8 and 9 at 1 and 5 min, respectively. At the time of writing, the baby was healthy and growing normally, with the exception of congenital pseudarthrosis.