Diaphragms and caps are barrier methods of contraception. They fit inside your vagina and prevent sperm from passing through the entrance of your womb (the cervix).
Diaphragms are soft, thin domes made of latex (rubber) or silicone. Caps are smaller and are also made of latex or silicone. They come in different shapes and sizes.
How they work
Diaphragms and caps stop sperm reaching an egg by covering your cervix. To be effective in preventing pregnancy, they need to be used in combination with spermicide, a chemical that kills sperm.
You only have to use a diaphragm or cap when you have sex, but you must leave it in for at least six hours after the last time you had sex (see Diaphragms and caps – how to use them). You can leave it in for longer than this, but should not take it out before.
How effective are diaphragms and caps?
If used correctly and in combination with spermicide, diaphragms and caps are estimated to be 92-96% effective in preventing pregnancy. This means if 100 women use a diaphragm or cap, between four and eight of them will become pregnant in one year.
There are other more effective contraceptives available, such as the oral contraceptive pill. Some women prefer to use diaphragms or caps because they do not like taking the pill. Others cannot take the pill for health reasons.
Diaphragms and caps only provide limited protection against sexually transmitted infections (STIs). If you are at a high risk of getting an STI - for example, if you or your partner has more than one sexual partner - you may be advised to use another form of contraception.
Cervix
The cervix is at the lower end of the womb. It connects the womb with the vagina.
Last updated: 04 October 2011
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