Range of contraceptive cervical caps, 20th century.
© Science Museum / Science & Society Picture Library
Cervical caps are thimble-shaped, soft rubber barriers that cover the cervix, blocking the opening to the uterus and preventing sperm from fertilising an egg. The groove on the inside of the cap creates a seal and keeps the cap in place together with support from the vaginal wall. Cervical caps must be left in place at least six hours after sexual intercourse has occured, but should not be left inserted for more than two days at a time (due to posible odour or irritation and posible asociation with an increased risk of toxic shock syndrome). This barrier method of contraception is effective when used in conjunction with a spermicidal cream or jelly applied to the cap, which immobilises the sperm.