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.