A contraceptive diaphragm or cap is a circular dome made of thin, soft silicone, although they come in different shapes, sizes and materials. You need to use it with a gel that kills sperm called spermicide. The most common active ingredient of spermicides is nonoxynol-9.
How the Cap or diaphragm works
A contraceptive diaphragm or cap is reusable and inserted into the vagina before sex. It is covered in spermicide (a gel that kills sperm) and prevents pregnancy by covering the cervix so sperm can’t get into the womb.
You need to go to your doctor or nurse to get fitted for a cap or diaphragm and it can take some time to learn how to use them.
They normally advise you wait until at least six weeks after having a baby before having a diaphragm or cap. You can have them after a miscarriage or abortion, but you may need to get a different size fitted.
Your doctor or nurse may give you a temporary cap or diaphragm to practice with at home, and will show you how to put in. You’ll need to go back to see them so they can check it’s the right size and that you can put it in properly. Whilst you practice you won’t be protected against pregnancy.
To insert a cap and diaphragm, you will be shown how to put spermicide on it, and to squeeze it between your finger and up inside the vagina. It’s important to check that your cervix is covered.
You need to make sure you don’t remove the cap or the diaphragm for at least six hours after the last time you had sex. You can leave them in up to 24 hours. After six hours has passed, you remove the cap or diaphragm by hooking your finger under its rim, loop or strap and gently pulling it down and out.
They are reusable – read the instructions for how to wash and look after it.
Most women can use the same diaphragm or cap for a year before they need to replace it. You may need a different size if you gain or lose more than 3kg in weight, or have had a baby.
How to stop
Stopping using cap or diaphragms is easy, you just don’t insert one before you have sex.
In general they have little to no after effects, but check out our survey results to see what others have experienced.
Things that can go wrong
The most common thing that can go wrong is that the cap doesn’t cover your cervix because it’s the wrong size or doesn’t fit properly. You may also accidentally remove the diaphragm or cap too soon – less than six hours after you had sex. If these things happen you may need to use emergency contraception.
There is a small chance you could develop toxic shock syndrome if the cap or diaphragm is left in for several days. This happens at a rate of 2.4 cases per 100,000 women using diaphragms, when it is left in for more than 24 hours.
Some women can be more likely to develop cystitis, bladder infections or bacterial vaginosis when they use a cap or diaphragm. If this happens your doctor or nurse can check the size as changing it to a smaller size may help.
Some people are sensitive to the chemicals in latex or spermicide
Like condoms, quite a lot of things can make diaphragms and caps less effective. If any of the following happen you should seek advice about emergency contraception:
If it gets damaged or has holes in it
You don’t use spermicide or extra spermicide when you use it or have more sex
You have sex three hours or more after you put it in and don’t use extra spermicide
Some oil based products (like oils and lotions) can damage latex based diaphragms or caps.