Diaphragms and caps

A diaphragm or cap covers the neck of your womb (cervix) and holds a reservoir of spermicide there to stop semen from being able to swim into your uterus to fertilise an egg.

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.

The device is kept in shape by a soft metal rim covered in latex or silicone. Your pelvic muscles hold the device in place. The device must be used each time you have sexual intercourse and left in for at least 6 hours after sexual intercourse.

When used with the correct technique and with spermicide, a diaphragm or cap has a success rate of about 94% (that is, 6 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, making it one of the less reliable methods of contraception.

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 your cervix if it is going to work properly. Correct fitting makes sure 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.

Before intercourse

You can put your diaphragm or cap in place up to 2 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

After intercourse wait at least 6 hours before removing your diaphragm or cap. If you have intercourse again within the 6 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 then dry it. Check each time for holes or thinning in the rubber. If you find any holes or thinning 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.

You should have your diaphragm or cap checked:

• every year
• after pregnancy, abortion or vaginal surgery
• if you gain or lose more than 3 kilograms of weight
• if you have any problems with it.

The advantages of using a diaphragm or cap include that they: 

• are used only when you have intercourse
• don't affect your menstrual cycle
• are non-hormonal
• have few side effects
• are easily reversible (as soon as you stop using one, your fertility returns)
• can be used safely while you are breastfeeding – but do not use it until after your first 6-week postnatal check
• can be used during your menstrual period to temporarily hold back the blood, making intercourse less messy
• should not be felt by your or your partner during intercourse.

• Diaphragms and cups are less effective at preventing pregnancy than other methods of contraception.
• They don't stop you from getting sexually transmitted infections.
• They are more expensive than other subsidised methods of contraception in New Zealand.
• Some women are allergic to latex 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, a diaphragm or cap in your vagina can irritate your bladder, causing cystitis (inflammation of your bladder).
• Caps should be renewed every year and diaphragms should be renewed every 2 years.