A study was carried out in order to determine the impact of Nomegestrol acetate on the human cervix and to evaluate the ability of changes induced in cervical mucus to render the cervical canal hostile to spermatoza at midcycle. Under the influence of Nom Ac, loss of spinability, absence of ferning pattern and drastic tightening of the glycoprotein meshwork rendered midcycle mucus very similar to that elaborated during physiological states under total progesterone dominance. The results obtained in this study gave clear evidence that Nomegestrol acetate may provide cervical blocking thereby preventing sperm transport to the uterine cavity.