During a normal monthly cycle, one of a woman's ovaries will produce a mature egg that will travel through the fallopian tube into the uterus. If sperm fertilizes this egg, the egg will attach itself to the uterine wall and begin developing into a fetus.

Barrier methods of birth control prevent pregnancy by making sure that sperm and egg do not meet.

The cervical cap is made of soft rubber. Like the diaphragm, it must be prescribed and fitted by a physician. Spermicide is placed in the base of the cap before insertion. Once inserted, a woman is protected from pregnancy for 48 hours. It should be removed by 48 hours in order to avoid the risk of toxic shock syndrome.

The diaphragm is available by prescription only and must be fitted by a physician. Once the diaphragm is fitted, a woman can insert and remove it by herself. This dome-shaped rubber disk protects from pregnancy in two ways. The diaphragm blocks sperm from entering the cervix. Spermicide jelly placed inside the rubber dome before insertion will kill any sperm it comes in contact with. Once inserted, the diaphragm is effective for up to six hours.

The female condom is a lubricated polyurethane sheath, similar in appearance to a male condom. It is inserted into the vagina. The closed end covers the cervix. Like the male condom, it is intended for one-time use and then discarded.

The sponge is inserted by the woman into the vagina and covers the cervix blocking sperm from entering the cervix. The sponge also contains a spermicide that kills sperm. It is available without a prescription.