The diaphragm or cap is a circular dome made of soft rubber which is put into the vagina to cover the neck of the womb (cervix), and prevent semen from getting through to fertilise an egg.
The device is kept in shape by a soft metal rim covered in rubber. The woman's pelvic muscles hold the device in place. The device must be used each time you have sexual intercourse.
When used correctly (and with spermicide), a diaphragm or cap has a success rate of about 96% (that is, four out of 100 women using diaphragms will get pregnant in any year). If not used correctly, the number getting pregnant can rise to 20 women out of 100.
Cervical caps are smaller than diaphragms, and are designed to fit more closely over your cervix. If you wish to use either device, you need to feel comfortable about inserting and removing it.
How do you use a diaphragm or cap?
A doctor or nurse will show you how to insert and remove a diaphragm or cap so that you can do it yourself. This first fitting is important as the diaphragm or cap must cover the whole of the opening of the cervix if it is going to work properly. Correct fitting ensures that the diaphragm or cap doesn't slip out of place during intercourse. You will be asked to practise for a week and then return to the doctor or nurse to make sure the size is correct. You can discuss any concerns at this time.
You can put your diaphragm or cap in place up to two hours before intercourse, so there is no need to interrupt sexual enjoyment. Before intercourse, insert your diaphragm or cap with about a teaspoon of spermicidal cream or jelly, which should be spread around the edge and the centre of the device.
After intercourse wait at least six hours before removing your diaphragm or cap. If you have intercourse again within the six hours you must apply more spermicide without removing the diaphragm or cap.
When you remove your diaphragm or cap, wash it with soap and water. Check each time for holes or thinning in the rubber. If you find them you will need a new diaphragm or cap. Store your diaphragm or cap in a place where you can easily find it each time - a cool place is best.
When to get the device checked
You should have your diaphragm or cap checked:
- every year
- after pregnancy or an abortion
- if you gain or lose more than three kilograms (half a stone)
- if you have any problems with it.
What are the advantages of using a diaphragm or cap?
- it is used only when you have intercourse
- it protects your cervix, so it can help prevent cancer of the cervix and some sexually transmitted diseases
- it does not affect your menstrual cycle
- it is non-hormonal
- there are few side-effects
- it can be used safely while you are breastfeeding - but do not use it until after your first postnatal check
- it can be used during your menstrual period to hold back the blood
- during your menstrual period intercourse is less messy
- if your diaphragm is correctly fitted, neither you nor your partner should be able to feel it during intercourse.
What are the disadvantages of using a diaphragm or cap?
- some women are allergic to rubber or spermicides
- you may have to interrupt sex to insert the diaphragm or cap
- it has to be used every time you have intercourse - it can't be left in place permanently
- in some women the diaphragm or cap in the vagina can irritate the bladder, causing cystitis (inflammation of the bladder)
- they must be renewed every year.
Where can you get a diaphragm or cap?
Diaphragms and caps are obtained from your doctor, a Family Planning centre, or a medical clinic or centre. Make sure that the health professional you see is trained and experienced in fitting them.
Diaphragms Family Planning, NZ, 2015