Probably the biggest drawback to spermicides IS that they have a fairly high failure rate .. Numerous studies have shown that this is a failure not so much of the products themselves (which are quite effective if used correctly) but of the way they're actually used. It's important to use spermicides every time you make love, and carefully follow the product instructions, but lots of people do so only haphazardly.

As a result, typical-use failure rates, for 100 women using spermicides for a
year, would result in about 20 pregnancies, according to a report from the Population Information Program at Johns Hopkins University in Baltimore. (Theoretically, if you used spermicides perfectly, every time, only about 3 preg¬nancies would occur.) By comparison, typical-use failure rates for sterilization are considerably less than 1 pregnancy per 100 women per year, about 3 for the Pill and the IUD and around 12 for condoms, according to Planned Parenthood.

It's really much better to use spermicides in combination with some other barrier method, like condoms, a diaphragm or a cervical cap. Even though some spermicidal products are marketed for use without any other form of backup birth control and can be used this way, you greatly reduce your chances of getting pregnant by "doubling up" your protection.