Contraceptive patch. Woman with a birth control patch attached to the skin of her abdomen, to prevent unwanted pregnancy. The patch continuously supplies norelgestromin (progestin) and ethinyl oestradiol (oestrogen) hormones to the bloodstream through the skin. These hormones, which are also found in contraceptive pills, suppress ovulation, meaning that the ovary does not release an egg and pregnancy is avoided. Each patch lasts for one week. Patches are worn for three weeks in succession, followed by one week with no patch. This patch is marketed with the trade name 'Ortho Evra'.