The cervical cap is a barrier method of birth control. It is a small rubber thimble-looking device which fits over the cervix, creating a suction seal and thus prevents sperm from entering the uterus.

The cervical cap is approximately 85-98% effective in preventing pregnancy. The effectiveness of the cervical cap is greatly increased when the woman knows how to use the cap correctly. This may take a little practice. We suggest that you practice insertion and check to make sure the cap is covering the cervix. Also check cap placement after intercourse the first few times to make sure it hasn't been knocked off the cervix during intercourse. If this happens, you may need a different size cap.

The package insert that accompanies the Prentif cervical cap recommends that a spermicidal cream or jelly be used in conjunction with the cervical cap, to insert the cap no more than one-half hour before intercourse and to leave the cap in no more than 48 hours. Most women use a teaspoon or so of either spermicidal jelly or cream in the cap. Many long time cap users leave the cap in place from one to seven days and don't bother to replenish the spermicide. It is important to remember that the cap must be left in place at least eight hours from the last intercourse to allow sufficient time for all of the sperm to die before the cap is removed.
Some women noticed that a foul odor accumulates in the cap. This is easily remedied by removing the cap, washing it (vinegar and water works well) and then putting it back in place, or letting the cap air out between wearing (soaking in vinegar and water works well).

It is also possible that a woman or her partner may be allergic to the rubber in the cap or to the spermicidal jelly or cream. You may need to switch spermicidal brands, use a natural spermicide or forego spermicide.
 
If you already know your size and need a replacement cap, you may Order a Cap through Women's Health Specialists.