Diaphragm (contraceptive)

The vaginal diaphragm is probably the safest form of female barrier contraceptive. It is a barrier of rubber or latex stretched across a circular rim that fits between the posterior fornix and the anterior vaginal wall just above the symphysis pubis thereby covering the cervix.

Spermicidal jelly should be placed on either side of the diaphragm which is inserted prior to intercourse (all caps require spermicide to achieve 95-97% effectiveness (1)). It should remain in position for at least 6 hours after intercourse so as to allow the spermicide to kill any spermatozoa.

However, it is inadvisable to leave the diaphragm in the vagina for more than 16 hours after intercourse as it becomes irritant and may lead to cystitis and vaginal colonisation by Staphylococcus aureus.

If there is poor vaginal tone or mild prolapse, lack of post-pubic shelf, or recurrent cystitis then the patient should be changed to a cervical cap (1).

Advantages:

• cheap
• woman can fit the device herself
• straightforward to use

Disadvantages:

• hypersensitivity to rubber or spermicide may preclude use
• high failure rate if poor fit
• anatomic variation may alter fitting - e.g. during pregnancy, due to age, uterine prolapse or perineal relaxation

A yearly replacement is recommended.

Reference:

• 1) Prescriber (2001), 12 (5), 83-95.