Combined oral contraceptives pils like Cilest work by over-riding the normal menstrual cycle. In a woman's normal menstrual cycle, levels of the sex hormones change throughout each month. The hormones cause an egg to be released from the ovaries (ovulation) and prepare the lining of the womb for a possible pregnancy. At the end of each cycle, if the egg has not been fertilised the levels of the hormones fall, causing the womb lining to be shed as a monthly period.
The daily dose of hormones taken in the pill work mainly by tricking your body into thinking that ovulation has already happened. This prevents an egg from ripening and being released from the ovaries each month.
Read the Patient Information Leaflet