Contraception. Abstract illustration of contracep tion, showing a uterus, egg cells (pink), and the menstrual cycle. On either side of the uterus are the fallopian tubes (with feathery tips) and ovaries (eggshaped), where eggs are produced. The red and pink pattern at the bottom symbolises the periodic shedding of the uterine lining during the menstrual cycle. The contraceptive pill, taken every day by millions of women, is almost 100% effective. It contains synthetic versions of the hormones oestrogen and progesterone, and works by blocking release of eggs from the ovaries and pre venting implantation of embryos in the uterus.