Mifepristone (RU486) and therapeutic late pregnancy termination: a double-blind study of two different doses.

An antiprogesterone, mifepristone (RU486), was administered to 35 patients undergoing a therapeutic interruption of pregnancy during the second and third trimester for maternal or fetal indications. A randomized double-blind study test was performed using 150 and 450 mg of mifepristone as pretreatment prior to prostaglandins. No toxicity or maternal morbidity were recorded. In three patients the onset of labour occurred spontaneously before prostaglandin administration. Mifepristone produced a modification in the consistency of the cervix with a statistical improvement in cervical calibration in the two groups, but the cervical effect was independent of the dose.