What is a diaphragm or cap and how is it used? – Doctors for Choice - Help Centre

A diaphragm is a circular dome made of thin, soft silicone that is inserted into the vagina before sex. It covers the cervix so sperm cannot enter the uterus and fertilise the egg. When used correctly with sperimicide, it is around 92% effective at preventing pregnancy. A similar contraceptive with a slightly different shape is called the cap. They come in different sizes and you should be examined by a nurse or doctor to ensure it is the right size for you before you use it.

Inserting a diaphragm

with clean hands, put 2 2cm strips of spermicide on the upper side of the diaphragm
put your index finger on top of the diaphragm and squeeze it between your thumb and other fingers
slide the diaphragm into your vagina, upwards – this should ensure that the diaphragm covers your cervix
always check that your cervix is covered – it feels like a lump, a bit like the end of your nose
if your cervix is not covered, take the diaphragm out by hooking your finger under the rim or loop (if there is one) and pulling downwards, then try again

Inserting a cap

with clean hands, fill one-third of the cap with spermicide, but do not put any spermicide around the rim as this will stop the cap staying in place
the cap has a groove between the dome and the rim – place some spermicide in this groove
squeeze the sides of the cap together and hold it between your thumb and first 2 fingers
slide the cap into your vagina, upwards
the cap must fit neatly over your cervix – it stays in place by suction
depending on your type of cap, you may need to add extra spermicide after it's been put in

You only have to use a diaphragm or cap when you have sex, but you must leave it in for at least 6 hours after the last time you had sex. You can leave it in for longer than this, but do not take it out before.

You need to apply more spermicide if:

you have sex again with the diaphragm or cap in place
the diaphragm or cap has been in place for 3 hours or more before you have sex

Do not take the diaphragm or cap out to reapply spermicide.

A diaphragm or cap does not provide reliable protection against sexually transmitted infections (STIs). If you're at a high risk of getting an STI, consider using condoms instead.

You should not use a diaphragm or cap during your period as there is a possible link with toxic shock syndrome (TSS), a rare condition that can be life threatening.