Diaphragm more effective contraceptive than sponge

Clinical question: 
How effective are the vaginal sponge and the diaphragm (used with a spermicidal cream) as contraceptives?
Bottom line: 
In a large US trial, for every 100 women who used the sponge for a year, about 17 became pregnant. Of those who used the diaphragm, 13 became pregnant. In a UK trial, for every 100 women who used the sponge for a year, about 25 became pregnant. Of the diaphragm users, 11 became pregnant. About 30% more women stopped using the sponge than the diaphragm. Allergy to the sponge was a problem for some women. However, discomfort caused about the same numbers of women to stop using either birth control method.
Caveat: 
The potential adverse effect of the spermicide nonoxynol-9, in high concentration in the vagina from sponge or diaphragm use remains a concern.1 Other randomised controlled trials will be needed to resolve the potential role of spermicides in preventing sexually transmitted infections or in causing adverse effects. The company manufacturing the sponge has filed for bankruptcy, so the continued availability of the sponge is uncertain at this time.
Context: 
The contraceptive vaginal sponge was developed as an alternative to the contraceptive diaphragm. The sponge, made of polyurethane impregnated with nonoxynol-9 (1g), releases 125mg of the spermicide over 24 hours of use. Unlike the diaphragm, the sponge can be used for more than 1 coital act within 24 hours without the insertion of additional spermicide, and the sponge does not require fitting or a prescription from a physician.
Review CD#: 
CD003172
PEARLS No: 
317
Date: 
October, 2008
Authored by: 
Brian R McAvoy