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What is a diaphragm and how effective is it? How is it different than a cervical cap?

Both the diaphragm and the cervical cap are rubber or silicone cups that fit inside the vagina and block the entrance to the cervix. They are barrier methods that prevent sperm from entering a girl or woman’s reproductive system and fertilizing an egg if there is one present.

Both methods are about 86- to 88-percent effective at preventing pregnancy with typical use. If used perfectly, they prevent pregnancy about 91 to 94 percent of the time.

In general, the diaphragm is wider and provides a looser fit. The cervical cap provides a much tighter fit because it creates a suction seal around the cervix. Both come in different sizes because the size of a cervix differs for each woman. To get either, a girl needs to be fitted by a doctor or other health care provider. A prescription is also required for both methods. Cost varies depending on where it is fitted and purchased.

To use a diaphragm or cervical cap, a girl puts spermicidal gel into the cup and around the edge and then inserts the diaphragm or cervical cap into the vagina before intercourse. The spermicidal gel provides a tight, sperm-killing barrier around the diaphragm or cervical cap. A diaphragm or cervical cap must be left in place for six to eight hours after intercourse. Having the diaphragm in for longer than 24 hours is not recommended, whereas the cervical cap can stay in for up to 48 hours before it is removed and cleaned.

In the case of the diaphragm or the cervical cap, girls can get irritation just from having the cap or diaphragm inside them or they may experience pressure against their bladder. The other downside is that in certain sexual positions, the diaphragm and cervical cap can slip out of position, which increases the chance of getting pregnant.

Neither method provides protection against sexually transmitted diseases (STDs), so a condom or other back up method should also be used.

For more information and photos of all the birth control methods, check out this FAQ.

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