The Diaphragm (Cap)

A contraceptive diaphragm or cap is a circular dome made of thin, soft silicone that’s inserted into the vagina before sex.

  • When used correctly with spermicide, a diaphragm or cap is 92-96% effective at preventing pregnancy.
  • You can put in a diaphragm or cap with spermicide any time before you have sex.
  • To be effective, diaphragms and caps need to be used with a spermicide. Spermicides are chemicals that kill sperm.
  • More spermicide is needed if it’s been in place for more than 3 hours.
  • The diaphragm or cap needs to be left in place for at least 6 hours after sex.
  • It can take time to learn how to use it.
  • Some women develop cystitis (a bladder infection) when they use a diaphragm or cap. Your doctor or nurse can check the size – switching to a smaller size may help.
  • The diaphragm does not provide protection against sexually transmitted infections.

How to Insert a Diaphragm

  • With clean hands, put two 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 isn’t covered, take the diaphragm out by hooking your finger under the rim or loop (if there is one) and pulling downwards, then try again.

How to Insert a Cap

  • With clean hands, fill one-third of the cap with spermicide, but don’t 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 two 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.