MODEL RELEASED. Contraceptive pills. Teenage girl popping a Trinordiol oral contraceptive pill out of a blisterpack. These pills are used for birth control. Here, different colour pills are taken at different times of the menstrual cycle. Numbers are present underneath each pill, instructing the user which pill to take on a particular day of her cycle. These contraceptive pills contain synthetic female sex hormones. Combined pills such as these contain forms of progestogen and oestrogen. Progestogens act on the pituitary gland affecting the menstrual cycle; oestrogen blocks the monthly release of a mature egg (ovulation).