The Skin Patch
The skin patch contains estrogen and progestin. The patch slowly releases these hormones through the skin over the course of seven days. The patch is changed weekly, but every fourth week is "patch-free" to allow menstruation. The patch is positioned on the buttocks, lower abdomen or the upper body.
Because of the possible link between estrogen and breast cancer, the patch should never be placed on the breast area.
The patch is 98 percent to 99 percent effective in preventing pregnancy.
Recent studies suggest that the total amount of estrogen absorbed during the month from the patch exceeds that from the combination oral contraceptive pill. There is some concern that the risk of blood clots is slightly increased in patch users compared with pill users. This potential risk must be weighed against any advantage of the patch when choosing this method of birth control.