Antiprogesterone effect and midcycle (periovulatory) contraception

Abstract

Based on the sequential changes of hormones in plasma and of progesterone binding sites in the uterus, it is suggested to give once a month, at midcycle (around ovulation), either progesterone itself or a parent compound binding to progesterone receptor. The aim is an antiprogesterone effect occurring presumably through a decrease of receptor functioning ultimately expressed some days later by lack of implantation.