A circular dome made of soft thin silicone that is inserted into the vagina before sex, covering the cervix so the sperm can't fertilise an egg
Perfect use: 92-96% effective. Between 4 and 8 women in 100 who use a diaphragm or cap with spermicide will get pregnant in a year.
Typical use: around 71-88% effective. Between 12 and 29 women in 100 using a diaphragm or cap will get pregnant in a year.