Minipill: A form of oral contraceptive taken daily, like combined oral contraceptives (the "pill"), but containing only the hormone progestin and no estrogen.
The minipill works by reducing and thickening cervical mucus to prevent sperm from reaching the egg. It also keeps the uterine lining from thickening, which prevents a fertilized egg from implanting in the uterus.
The minipill is slightly less effective in preventing conception than the pill.
The minipill can decrease menstrual bleeding and cramps as well as diminish the risks of endometrial and ovarian cancer and pelvic inflammatory disease. Because the minipill contains no estrogen, it does not present the risk of blood clots associated with estrogen in combined pills.
The minipill is a useful option for women who cannot take estrogen because they are breast-feeding or because estrogen-containing products cause them to have severe headaches or high blood pressure.
The side effects of the minipill include menstrual cycle changes, weight gain, and breast tenderness.