A diaphragm is a shallow, dome-shaped cup made of silicone that you insert into your vagina before sex to cover your cervix and physically block sperm from reaching an egg. With perfect use, it prevents pregnancy about 94% of the time. With typical use, that number drops to around 87%, mainly because people sometimes skip it or don’t position it correctly.
It’s one of the few non-hormonal, reusable birth control options available, which makes it appealing if you want to avoid the side effects that come with hormonal methods like the pill, patch, or IUD.
How a Diaphragm Works
The diaphragm acts as a physical barrier. When placed correctly, it sits snugly over your cervix (the narrow opening at the bottom of your uterus) so sperm can’t pass through. You always use it with spermicide, a gel or cream that kills or immobilizes sperm on contact. You apply the spermicide to the inside of the dome and around the rim before inserting it. The combination of the barrier and the spermicide is what gives the diaphragm its effectiveness.
Unlike condoms, a diaphragm doesn’t protect against sexually transmitted infections. It only prevents pregnancy.
Types of Diaphragms
There are two main types available. Traditional diaphragms, like the Milex brand, come in multiple sizes and require a clinician to measure you during a pelvic exam. The provider determines the right diameter for your anatomy and writes a prescription for that specific size.
The newer option is the Caya diaphragm, a single-size contoured design that fits most users without a custom fitting. Its shape is slightly different from the classic round dome, with a more anatomical contour and a finger notch that makes removal easier. Caya still requires a prescription in most places, but the process is simpler since there’s no sizing appointment.
How to Insert and Remove It
You can insert a diaphragm up to two hours before sex. Apply about a tablespoon of spermicide to the dome and rim, then fold the diaphragm in half, slide it into your vagina, and push it up toward your cervix. Once in place, you should be able to feel the cervix through the silicone. If you can feel the rim sitting securely behind your pubic bone and covering the cervix completely, it’s positioned correctly. You shouldn’t be able to feel it during sex.
After sex, the diaphragm needs to stay in place for at least six hours. This gives the spermicide enough time to neutralize any sperm. If you have sex again before the six hours are up, add more spermicide without removing the diaphragm. Don’t leave it in for more than 24 hours total, as prolonged wear increases the risk of infection.
To remove it, hook a finger under the rim and pull it out gently. Wash it with warm water and mild soap, let it air dry, and store it in its case.
Effectiveness: Perfect vs. Typical Use
The gap between perfect and typical use matters more with a diaphragm than with many other methods. Under ideal conditions, with correct placement and consistent spermicide use every single time, the failure rate is about 6% per year. In real-world use, roughly 13 to 16 out of 100 people using a diaphragm will become pregnant in a given year.
Most failures come down to user error: inserting it incorrectly, forgetting the spermicide, removing it too soon, or skipping it altogether during spontaneous sex. If you’re someone who prefers a method you don’t have to think about in the moment, a diaphragm may not be the best fit. But if you’re comfortable with the routine and use it consistently, it’s a solid option, especially paired with other awareness-based strategies like cycle tracking.
Benefits of Using a Diaphragm
The biggest draw is that it’s completely hormone-free. You won’t experience the mood changes, weight fluctuations, or other systemic effects that some people have with hormonal contraception. It also doesn’t alter your menstrual cycle or fertility. The moment you stop using it, your ability to conceive returns to normal immediately.
A diaphragm is reusable, which makes it cost-effective over time. A single device typically lasts one to two years with proper care. You only use it when you need it, so there’s nothing to take daily and nothing implanted in your body. You control it entirely on your own terms.
Side Effects and Risks
Diaphragms are generally safe, but there are a few things to be aware of. The most common issue is an increased risk of urinary tract infections. The rim of the diaphragm can press against the urethra, which may make it easier for bacteria to cause infection. If you’re prone to UTIs, this is worth considering.
Some people experience irritation from the spermicide rather than from the diaphragm itself. Nonoxynol-9, the active ingredient in most spermicides, can irritate vaginal tissue, especially with frequent use. This irritation can also affect a partner. If you notice burning or discomfort, switching to a different spermicide formulation may help.
Toxic shock syndrome is a rare but serious risk associated with leaving a diaphragm in for too long. Sticking to the 24-hour maximum and removing it as soon as the minimum six-hour window has passed keeps this risk very low.
Who It Works Best For
A diaphragm tends to work well for people who are comfortable touching their own body and don’t mind the routine of inserting it before sex. It’s a good choice if you have sex relatively infrequently and want birth control only when you need it, rather than something that’s always active. It’s also useful as a backup method alongside cycle tracking or withdrawal.
It may not be the best option if you have frequent UTIs, are sensitive to spermicide, or find it difficult to plan ahead before sex. People who’ve recently given birth or had pelvic surgery should be refitted, since changes in anatomy can affect how well the diaphragm sits over the cervix. Significant weight changes of 15 pounds or more can also shift the fit.
How to Get a Diaphragm
In most countries, you need a prescription. For a traditional diaphragm, this involves a pelvic exam where a clinician determines your size using fitting rings. For the Caya one-size model, a provider can often write the prescription after a standard visit without a separate fitting. Some telehealth services now prescribe Caya after a brief consultation, making access easier than it used to be.
Once you have the prescription, diaphragms are available through pharmacies or online retailers. The cost varies, but since a single device lasts up to two years, the ongoing expense is mainly the spermicide. Many insurance plans cover the device and the fitting appointment as part of contraceptive coverage.