How it works
The device sits over the cervix (the entrance to the womb) and blocks sperm from getting in. Spermicide, a gel that stops sperm moving, is usually used with it for extra protection.
People who want a hormone-free method they use only when having sex and are comfortable inserting it.
How effective is it?
Typical use
83%
In real life about 17 in 100 people get pregnant in a year with typical use.
Perfect use
84%
About 16 in 100 when used exactly as directed every time.
Figures are for the diaphragm used with spermicide; the cap can be less effective, especially after giving birth
See how it ranks against every method in the effectiveness chart.
How to use it
Get the right type and size from a sexual health clinic or doctor; some diaphragms come in one size, while others need fitting by a nurse or doctor.
Put spermicide on the device as instructed and insert it before sex, checking that it covers your cervix.
If you have sex again, or it was put in more than a few hours earlier, add more spermicide without taking the device out.
Leave it in for at least 6 hours after the last time you had sex, but not longer than the instructions say.
Wash it in mild soap and warm water, let it dry and check it for holes or tears before storing it in its case.
Pros and cons
Advantages
- No hormones and no effect on periods
- Only used when you have sex, and can be put in beforehand
- Reusable, so one device lasts a long time
- You can stop using it at any time, and fertility is not affected
- Suitable while breastfeeding
Disadvantages
- Less effective than many other methods, especially if not used every time
- Does not protect against STIs, so condoms are still needed for that
- Takes practice to insert and check correctly
- Spermicide can be messy and may irritate
- Can be hard to find in some countries
Effect on periods: No effect on periods, but don't use it during your period.
Possible side effects
- Irritation or soreness from spermicide or the device
- Bladder infections (UTIs) in some users
- Vaginal irritation or allergy to silicone or spermicide (rare)
Who it may not suit
A clinician checks your medical history before you start. This list is not complete.
May not be suitable if
- You have had toxic shock syndrome
- You get frequent urinary tract infections
- You have weak vaginal muscles or a prolapse, or your cervix is an unusual shape or position
- You are at high risk of HIV, because frequent use of spermicide containing nonoxynol-9 can irritate the vagina and may raise the risk of HIV infection
- You have recently given birth, miscarried or had an abortion (you may need to wait and be refitted)
Get medical help if
- You have a sudden high temperature, a rash like sunburn, vomiting or feel faint while using it (possible toxic shock syndrome; remove it and get urgent help)
- You have pain, burning when you pee or unusual discharge
- You have gained or lost a lot of weight, or have given birth, as you may need a different size
Frequently asked questions
How effective is a diaphragm?
With typical use about 17 in 100 people get pregnant in a year using a diaphragm with spermicide. Using it correctly every single time makes it more effective, but it is still less effective than methods like the implant or IUD.
How long do I need to leave a diaphragm in after sex?
Leave it in for at least 6 hours after the last time you had sex. Don't leave it in for longer than the instructions for your device say, because of the small risk of toxic shock syndrome.
Do I have to use spermicide with a diaphragm?
Most guidance recommends using spermicide with a diaphragm or cap, and effectiveness figures are based on that. Spermicide containing nonoxynol-9 can irritate the vagina, and the WHO advises that people at high risk of HIV should not use it often.
Do I need to be fitted for a diaphragm?
Some diaphragms come in one size that fits most people, while others and most caps need a nurse or doctor to find the right size. You may need a new size after giving birth or a big change in weight.
Does a diaphragm protect against STIs?
No. A diaphragm or cap does not reliably protect against STIs, so use condoms as well if you are at risk.
Sources
Reviewed 1 November 2026. We link to the guidance itself so you can check it.