Contraceptive Diaphragms & Caps

A cap or diaphragm is a type of contraception used by women to prevent pregnancy. It is a thin, silicone dome or bowl designed to block the passage of sperm in a similar way to a condom. However, unlike a condom, a contraceptive cap is inserted inside the vagina to cover the cervix.


How the contraceptive diaphragm works

The contraceptive diaphragm is a barrier method of contraception. This means it physically puts a barrier in place to prevent the fertilisation of eggs. By blocking the cervix, the diaphragm or cap stops sperm from entering the uterus, so it cannot reach an egg to fertilise it. However, this alone may not prevent pregnancy.

You must also use a gel called spermicide when using a contraceptive cap. This gel helps to kill sperm, which ensures that the sperm cannot fertilise an egg. If you do not use a spermicide gel while using a contraceptive diaphragm, it may not be as effective and you may not be protected against pregnancy.

Despite being a barrier method of contraception, diaphragms or caps do not give full protection against sexually transmitted infections (STIs). To get this protection, you should use a condom as well as your cap or diaphragm.


How to use a contraceptive diaphragm

A contraceptive diaphragm can be inserted any time before you have sex, but it must remain in place for at least 6 hours after sex. This allows time for the spermicide to take action before you remove the diaphragm. You can leave the diaphragm in place for longer than 6 hours, but you shouldn’t leave it for more than 30 hours. In the case of caps, the maximum time is 48 hours.

Additionally, you shouldn’t use a contraceptive cap or diaphragm when you are on your period, as it could lead to toxic shock syndrome (TSS). While rare, TSS can be life-threatening.

You should apply spermicide to your cap or diaphragm before you insert it, making sure to read the instructions carefully. It’s important to check that the diaphragm or cap is in place over your cervix before you have sex - if it’s not, you might not be protected. Your cervix feels like a lump similar to the end of your nose.

If your diaphragm or cap is in place for more than three hours before you have sex, or if you intend to have sex again, you’ll need to apply more spermicide. Do not remove the cap or diaphragm to reapply spermicide.


How to look after a diaphragm or cap

Taking care of your contraceptive cap or diaphragm is key to keeping it in good condition. You should clean your diaphragm or cap after use in mild unscented soap and warm water. Make sure to rinse all the soap off it, and then let it air dry.


  • Use oil-based products such as lubricants or cleaning agents
  • Use boiling water
  • Use harsh cleaning fluids, disinfectants, detergents or talcum powder
  • Use your diaphragm or cap without checking for damage

You will likely need to get a new diaphragm or cap at least once a year. If you gain or lose more than 3kg of weight, have an abortion or miscarriage or give birth, you may need to get a different size of cap. A doctor or nurse can advise you on which size is right for you.


What to do if you forget to use a contraceptive diaphragm

 If you have sex without contraception, you may need to use emergency hormonal contraception. This also applies if you have sex with a diaphragm or cap and:

  • It is damaged or the wrong size
  • You forget to reapply spermicide to have more sex, or don’t use spermicide at all
  • You remove it before the minimum 6 hours after sex are up
  • You use any products that can damage the latex, e.g. oil-based lubricants


Who can use a contraceptive diaphragm?

Contraceptive diaphragms or caps are suitable for many, however there are certain circumstances which may mean it isn’t right for you. These include if you have:

  • Suffered from toxic shock syndrome before
  • Had repeated or recurring urinary tract infections (UTIs)
  • A current vaginal infection - you should wait for the infection to clear up prior to using a cap or diaphragm
  • High risk for STIs
  • Weak vaginal muscles that cannot hold the diaphragm or cap in place (possibly as a result of childbirth)
  • An allergy or sensitivity to latex or chemicals contained in spermicide
  • An unusually positioned or shaped cervix, or if you can’t reach your cervix

It is also recommended that you do not use a diaphragm or cap within 6 weeks of giving birth or having a miscarriage or abortion. If you’re unsure which contraception is right for you, consult a pharmacist who can give you advice.


How effective is the contraceptive diaphragm?

If used correctly, including the application of spermicide, a contraceptive cap or diaphragm is between 92% and 96% effective. This, of course, depends on you remembering to use contraception every time you have sex, leaving the diaphragm or cap in for at least 6 hours after sex and remembering to reapply spermicide if you intend to have sex again.

It can take time to learn how to properly use a contraceptive diaphragm or cap, so you may find it beneficial to use additional contraception until you are confident.


Common side effects of contraceptive diaphragms

Sometimes, for some women using a contraceptive cap or diaphragm can result in a bladder infection or cystitis. Additionally, spermicides and latex diaphragms can cause discomfort, irritation or allergic reactions. However, if used correctly, there aren’t any significant risks to health associated with the use of contraceptive diaphragms or caps.

Diaphragms and caps are also not affected by any medications you may be taking. As non-hormonal forms of contraception, they do not affect your menstrual cycle - but if you intend to have sex during your period, you will need an alternative contraceptive instead of your cap or diaphragm.


Where to get contraceptive diaphragms

Like many other types of contraception, contraceptive caps or diaphragms can be sourced from contraception or family planning clinics, sexual health clinics, GP surgeries and some young people’s services. , You may be given a temporary version initially. This allows you to test the size and get used to putting one in.

After this, you can return to get a proper diaphragm or cap. You should wear it to this appointment so that the doctor or nurse can check you’re wearing it correctly and that the size is right. Going forward, you can then get replacement caps or diaphragms from these services as well.