The diaphragm also may provide a barrier to STDs. If used with a condom, the effectiveness rate is almost 100 percent. Occasionally minor vaginal irritation may occur. It cannot be used during menses. If a woman gains or loses 10 pounds or more, her diaphragm must be refitted.
Caps are smaller than diaphragms and made of thicker rubber.
They come in only four sizes and are hard to fit to women who already have had a vaginal delivery. About 50 percent of women can be fit successfully for a cap. It is held in place by the snug fit and by suction. The cap provides continuous protection for 48 hours, no matter how many times intercourse occurs. Unlike diaphragm use, additional jelly is not needed for repeated intercourse, but cap position should be checked after each act of sex.