Focused-Ultrasound Termination of an Early Pregnancy in Rhesus Macaques (Macaca mulatta): A Pilot Study

We explored the effectiveness, safety, and feasibility of focused ultrasound in terminating undesired pregnancy. A high-intensity focused ultrasound therapeutic unit was employed to terminate early pregnancies in rhesus macaques. B-mode ultrasound incorporated within the system was used to locate and study the gestational sacs of 6 rhesus macaques with gestation ages of 37 to 66 days, and varying modes of ultrasound exposure were adopted in the termination of the early pregnancies of the rhesus macaques. After focused ultrasound exposure, B-mode ultrasound of the gestational sacs showed significant lethal changes. Of the 6 rhesus macaques, 5 underwent complete abortions whereas 1 rhesus macaque underwent an incomplete abortion. The rhesus macaques resumed their menstrual cycles 50 days after focused-ultrasound treatment. The results suggested that focused ultrasound could be safe, feasible, and effective in terminating early pregnancies in rhesus macaques. As a novel physical method, it may be a promising ablation for a potentially clinical application.