How does Marvelon work?
Birth control pills such as Marvelon help reduce the chances of pregnancy in two ways.
Firstly they inhibit your monthly release of an egg(s) by your ovaries. Secondly, studies suggest that changes in the endometrium (lining of the womb) and mucus produced by the cervix (opening of the uterus) occur with the use of birth control pills.
The combined effect is to make it less likely that a sperm will penetrate an egg, or for an egg to implant on the wall of the uterus.