How does the diaphragm work?

A diaphragm is a flexible cup that you insert into your vagina up to 3 hours before sex. When it’s properly in place, it covers your cervix and keeps sperm in the vagina. The spermicide used with the diaphragm will stop the sperm from reaching your womb to fertilise an egg.

Used correctly, a diaphragm is 92–96% effective against pregnancy. With typical use (in other words the way it’s usually used, which isn’t always perfect) it’s 88% effective.

It does not protect you against sexually transmitted infection.

Using a diaphragm to stop pregnancy

Diaphragms traditionally came in different sizes, and your first one needed to be fitted by a trained health professional.

Now there’s a one-size silicone type that you can get from a pharmacy without fitting. It fits most people. But it can take time to get used to using a diaphragm correctly. It’s a good idea to practise putting in your diaphragm before you use it for the first time.

You need to leave your diaphragm in place for at least 6 hours after you’ve finished having sex. This is to make sure sperm can’t get to your womb in the time afterwards. You can leave it in longer than 6 hours, but not longer than 24 hours.

Spermicide needs to be applied again:

  • if you have sex again – with the diaphragm still in place

  • if the diaphragm has been in for more than 2 hours before you have sex (you can take it out to reapply the spermicide if you haven’t had sex yet, or you can use an applicator to apply more while it’s in place)

What is spermicide?

Spermicide is a chemical that stops sperm from reaching an egg. You need to put it inside the vagina. It’s available as a gel, cream or foam. When using a diaphragm, spermicide gel is put on the diaphragm before you insert it.

You can get spermicide gel at a pharmacy or a sexual health clinic. You can also use spermicide with condoms for extra protection.

The active ingredient in most spermicides is nonoxynol-9. But there are now contraceptive gels available to use with your diaphragm that do not contain nonoxynol-9. These are a good option if you’ve had a reaction or irritation when using spermicide.

Everything you wanted to know about sexual health and wellbeing - your questions answered by our expert team.