All spermicides contain an ingredient, usually nonoxynol-9, that immobilizes or kills sperm on contact. Spermicides provide a mechanical barrier and need to be placed into the vagina before each coital act. Their effectiveness increases with increasing age of the women who use them, probably due to increased motivation. The effectiveness of spermicides is similar to that of the diaphragm, and increases with the concomitant use of condoms.