Effectiveness depends on the user: Risk of pregnancy is greatest when spermicides are not used with every act of sex.

• One of the least effective family planning methods.
• As commonly used, about 21 pregnancies per 100 women using spermicides over the first year. This means that 79 of every 100 women using spermicides will not become pregnant.
• When used correctly with every act of sex, about 16 pregnancies per 100 women using spermicides over the first year.

Return of fertility after spermicides are stopped: No delay

Protection against sexually transmitted infections (STIs): None. Frequent use of nonoxynol-9 may increase risk of HIV infection (see Question 3).