Which of the following statements is true regarding spermicides found in vaginal foams, creams, and suppositories?

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. Although it has been repoed that contraceptive failures with spermicides may be associated with an increased incidence of congenital malformations, this finding has not been confirmed in several large studies and is not believed to be valid. Levonorgestrel is a synthetic progestational agent found in several combination oral contraceptive pills.