P09.23: A clinical trial of ultrasound treatment for TRAP sequence

We present a case of TRAP sequence for which high-intensity focused ultrasound (HIFU) was applied as a non-invasive fetal therapy. Case; A 23-year-old woman was admitted to our hospital at 22 gestational weeks. Ultrasonography led to a diagnosis of TRAP sequence. Neither hydramnios nor signs of heart failure were identified in the normal fetus, but because the anomalous fetus displayed pronounced subcutaneous edema, the decision was made at 26 gestational week to apply ultrasound-guided HIFU exposure to occlude the vessel and interrupt the blood flow of the anomalous fetus. The Ethics Committee for Clinical Studies approved the procedure and consent was obtained from the patient after explanation. Target for HIFU exposure was the internal blood flow at the point where the umbilical cord entered the body of the anomalous fetus. Exposure was performed multiple times and decreased blood flow was confirmed by Doppler color imaging; however, complete occlusion was not achieved. Despite the failure of complete occlusion, a hyperechoic area was observed just proximal to the target blood; this finding indicated degeneration of the tissue by exposure to HIFU. Collateral damage was not seen in either the pump fetus or the mother's body. Polyhydramnios appeared at 29 gestational weeks, thus making premature birth an imminent threat. Therefore, a cesarean section was performed. The pump fetus weighed 845 g, the anomalous fetus weighed 2800 g. After 9 months, the survival baby does not have severe clinical complication and mother does not have any complications. The concept of the present treatment using HIFU does not involve insertion of a device into the uterus and enables thermal denaturation of the fetal tissue without any direct fetal contact. Although the procedure was not completely successful in this case, the possibility of inducing localized denaturation of human fetal tissue has been demonstrated, thus marking a step toward the future use of HIFU in fetal treatment.