The diaphragm has a dual mechanism to prevent a pregnancy. A dome-shaped rubber disk with a flexible rim covers the cervix so sperm cannot reach the uterus and a spermicide applied within the diaphragm before insertion kills sperm.
A diaphragm protects against conception for six hours. For intercourse after the six-hour period, or for repeated intercourse within this period, fresh spermicide should be placed in the vagina with the diaphragm still in place. The diaphragm should be left in place for at least six hours after the last intercourse
A diaphragm should not be left in place for more than a total of 24 hours because of the risk of toxic shock syndrome (TSS), a rare but potentially fatal condition. Symptoms of TSS include sudden fever, stomach upset, a sunburn-like rash, and a drop in blood pressure.