[The effects of an antiprogesterone steroid in women: interruption of the menstrual cycle and of early pregnancy].

RU-486 is a steroid which possesses a great affinity for the progesterone receptor, does not have a progesterone activity, but is indeed a strong antagonist of progesterone effects in animals. Oral administration induces the interruption of the luteal phase of the menstrual cycle and that of early pregnancy in women. Its mode of administration and its properties enable us to envisage a new methodology for menstrual cycle regulation and human birth control.