This article on diaphragms and caps explains how they work, who they are suitable for and the advantages & disadvantages of diaphragms and caps.

Note: Diaphragms and caps are not really available in New Zealand anymore as people tend to prefer IUDs or other  forms of contraception. It is no longer possible to buy spermicide from pharmacies in New Zealand. 

What are diaphragms and caps?

Diaphragms and caps are made out of rubber and are shaped to fit over your cervix,  at the top of your vagina, preventing sperm entering your womb and reaching the egg to fertilise it after sexual intercourse.


These are larger and circular and maintain their shape by a metal ring, which is covered with rubber.


These are smaller and fit more snugly over your cervix. There are different types of caps.

Where can you get diaphragms and caps?

Diaphragms and caps can be fitted and supplied by your local Family Planning Centre or by your doctor. They should only be fitted by health professionals who have been trained to do so, or they will not be so reliable.

How do diaphragms and caps work?

  • Diaphragms and caps work in conjunction with spermicide jelly (Gynoll II is available in New Zealand). This is applied to your cap or diaphragm prior to sex, the cap/diaphragm is put in place in your vagina by inserting it with your finger, to ensure it is covering your cervix.
  • Therefore the entrance to your womb (the cervix) is blocked, hence preventing the sperm reaching your egg in your fallopian tube. The spermicide jelly kills the sperm, therefore ensuring that no sperm sneak past! The Family Planning centre will supply a spermicide jelly.
  • The diaphragm/cap must be kept in place for at least 6 hours after sex, when it is then removed with your finger, washed and is ready to be used again.

What is the success rate of diaphragms and caps?

Diaphragms and caps have a success rate of 96%. If 100 women use the cap/diaphragm correctly, every time they have sex, 4 will fall pregnant in one year.

Diaphragms and caps do NOT prevent sexually transmitted infections or STIs. It is necessary to use a condom also to prevent infection.

What are the risks of diaphragms and caps?

  • The success rate in preventing pregnancy is comparatively lower than other methods of contraception, therefore it possible less suitable for younger, more fertile women, where pregnancy would be unwanted.
  • It is possible that the spermicide may irritate your vagina or even cause an allergic reaction.
  • It is possible that the cap/diaphragm makes you more prone to bladder irritation/infection.

What are the pros?

  • Diaphragms and caps cover the cervix, therefore they may reduce the rate of catching some sexually transmitted infections and the rate of cervical cancer.
  • There are no hormones in this method of contraception and therefore your normal menstrual cycle is not affected.
  • It is immediately reversible, by simply stopping using it.
  • Sex during your period will be less messy.
  • Neither you nor your partner should be aware of the diaphragm/cap during sexual intercourse.

What are the cons?

  • You must use the cap or diaphragm every time you have sex, in order for it to have maximum protection against pregnancy.
  • Annual check ups are necessary, to ensure the cap is fitting well. This check up should be more frequent if you have gained or lost more than 3kg or had a baby.

Useful websites & articles

For additional information on Condoms, click here.

To compare this contraceptive with the Combined Pillor Progesterone Only / Mini Pill, visit our informative articles.

To find your local Family Planning Clinic in NZ visit- www.familyplanning.org.nz

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Paula Skelton is a qualified NZ nurse and midwife, a midwifery & childbirth educator and the mum of three lovely girls.

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