Diaphragms, one of the birth control methods, are soft latex devices (cup with a flexible rim) and block the cervix.
The devices are inserted into the vagina of the woman and fitted behind the pubic bone and over the cervix, so that they cover the cervical opening and prevent sperm from entering into the uterus.
Diaphragm can be inserted sometime before intercourse and should be left in the vagina for 6 - 8 hours after sexual relations.
They are fairly effective if inserted correctly and used with spermicidal jelly/cream more to the point they don't interfere with a woman's natural cycle.
Diaphragms don't protect against sexually transmitted disease.
A person having allergic to latex should avoid the use of latex diaphragm, besides these are linked with increased risk of urinary tract infection.