When fully inserted, the rim of this flexible cup (made of latex or medical silicone) sits an inch or so behind the pubic bone, and the rest of the rubber ring then naturally expands into a soft elliptical shape and settles against the front wall of the deepest part of the vagina, surrounding the cervix. It is most effective when used in tandem with spermicide, but if used alone, it is far more effective than spermicide alone. The spermicide should be applied just before insertion, and should be applied to the centre of the dome (which contacts the opening of the cervix) and around the contact surface of the rim.
Diaphragms are different from cervical caps, which are smaller, thimble-shaped and placed directly over the cervix. Some women with especially long (or rather, deep) vaginas may find it difficult to position cervical caps properly, as their cervixes may be too far back to reach easily. In these cases, using a diaphragm may be more comfortable. The latest variation on diaphragms and cervical caps is Lea's shield, a one-size-fits-all device which stays in place because of suction at the end of the vagina and by this covering the cervix.
The diaphragm is an option for couples in which the woman cannot use hormonal forms of contraception (including the pill, norplant, and Depo Provera) for any of a variety of reasons, including having recently undergone a minor cervical procedure (e.g. abnormal cell removal).
Diaphragms have advantages and disadvantages when compared to condoms. It does require a little forward-thinking on the part of the woman to insert her diaphragm if she feels that intercourse is likely soon. However, once inserted, intercourse can commence at any time during the next several hours without any pause to apply the condom between foreplay and intercourse. Unlike with condoms, there remains direct intimate skin-to-skin contact, and so the diaphragm does not impair the natural physical sensations of sexual intercourse for either partner. Unlike condoms, diaphragms do not protect against STDs.
Diaphragms can lead to an increased risk of Urinary Tract Infections, cystitis, and the rare Toxic Shock Syndrome. Although the reasons for this are not fully understood, some evidence suggests these are reactions to the spermicide used in the diaphragm, rather than the device itself. Alternative explanations include pressure from the rim of the diaphragm pushing on the neck of the bladder, or the diaphragm trapping bacteria and secretions in the vagina.
Diaphragms made of latex must not be used with oil-based lubricants, as they may cause the latex to weaken and crack. Water-based lubricants are safe for use with latex, and are available in most pharmacies.
