Both the cervical cap and the diaphragm are rubber cups that fit inside the vagina and block the entrance to the cervix. They are barrier methods that prevent the sperm from swimming into the female’s reproductive system and fertilizing an egg if there is one present. In general, the diaphragm is wider but provides a looser fit. Read more below about how this can be addressed. 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. A health care provider will determine the best size during a pelvic exam.

To use the diaphragm, a girl puts spermicidal gel around the edge of the it, and then inserts the diaphragm into the vagina before intercourse. The spermicidal gel provides a tight, sperm-killing barrier around the diaphragm. The diaphragm must be left in place for six to eight hours after intercourse, whereas the cervical cap can stay in for up to 48 hours before it is removed.

Both methods offer NO protection against sexually transmitted diseases (STDs), so a condom or other back up method should also be used.

Both methods are about 80 to 85 percent effective at preventing pregnancy with typical use. If used perfectly, they prevent pregnancy about 94 percent of the time.

Sometimes, males and females can be allergic to the spermicides. 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.

The diaphragm is a good choice for girls who can always plan when they will have sex so they know when to have the diaphragm and spermicide with them, feel comfortable putting the diaphragm inside their vagina and can’t or don’t want to use hormonal contraception.

To get either, a girl needs to be fitted by a doctor or other health care provider. A prescription is also required. Cost varies depending on where it is fitted and purchased.

For more information and photos of all the birth control methods, go to the story “An A to Z of Contraception” by Claire Marchetta, 18, Staff Writer.