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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 silicone cups that fit inside the vagina and block the entrance to the cervix. They are barrier methods that prevent sperm from entering through the cervix and fertilizing an egg.

Both methods are about 71 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 fits a little more loosely. The cervical cap fits more tightly because it creates a suction seal around the cervix. Both come in different sizes because the size of a cervix differs from person to person. To get either, you need to be fitted by a doctor or other health care provider. A prescription is also required for both methods. The cost varies depending on where the method is fitted and purchased.

To use a diaphragm or cervical cap, you put spermicidal gel into the cup and around the edge and then insert 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 at least six 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, irritation is possible just from having the cap or diaphragm inside the vagina or there may be pressure against the 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 using a condom too will protect you against STDs.

For more information about all the birth control methods, check out this FAQ.

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