The cervical cap is a birth control (contraceptive) device that prevents sperm from entering the uterus. The cervical cap is a reusable, deep silicone cup that is inserted into the vagina and fits tightly over the cervix. The cervical cap is held in place by suction and has a strap to help with removal.The cervical cap is effective at preventing pregnancy only when used with spermicide. Only one cervical cap - FemCap - has Food and Drug Administration approval in the U.S. It must be fitted and prescribed by a health care provider.