Mechanisms of action of oral contraceptive pill Suppresses pituitary hormones, FSH and LH peak and through their suppression prevents ovulation. Progestogen causes atrophic changes in the endometrium and prevents nidation. Progestogen also acts on the cervical mucus making it thick and tenacious and impenetrable by sperms. Increases the tubal motility, so the feilized egg reaches the uterine cavity before the endometrium is receptive for implantation.