A diaphragm is a dome-shaped silicone or rubber cup that you insert into the vagina before sex to physically block sperm from reaching the cervix. Used with spermicide, it has a typical-use failure rate of about 17%, meaning roughly 17 out of 100 people using it over a year will become pregnant. It’s one of the few non-hormonal, reusable birth control options available, which makes it appealing to people who want to avoid hormonal side effects or who only need contraception occasionally.
How a Diaphragm Prevents Pregnancy
The diaphragm works in two ways. First, it sits over the cervix and acts as a physical barrier, stopping sperm from entering the uterus. Second, spermicide gel or cream applied inside the dome before insertion kills sperm on contact. Neither mechanism alone is considered reliable enough on its own, which is why the two are always used together.
Because no hormones are involved, the diaphragm doesn’t affect your menstrual cycle, suppress ovulation, or alter your hormone levels. That makes it safe for people with medical conditions that rule out estrogen-based methods, and it’s also compatible with breastfeeding.
Traditional Fitted vs. One-Size Diaphragm
Traditional diaphragms come in multiple sizes and require a pelvic exam so a provider can determine the right fit. The FDA classifies these as prescription-only devices, and they need to be checked at intervals to make sure they still fit correctly, particularly after pregnancy or significant weight change.
A newer option called the Caya diaphragm is the first new design to enter the U.S. market in over 50 years. It uses a contoured shape with a nylon spring and silicone cup that fits most people without a sizing exam. Clinical studies confirmed that the single-size design works for the majority of people who could wear a traditional fitted diaphragm. While a prescription is still required in the U.S., the elimination of the fitting exam makes access significantly easier.
How to Use It
You apply a tablespoon of spermicide to the inside of the cup, then fold the diaphragm and insert it into the vagina so it covers the cervix. It can be placed up to a couple of hours before sex. If you have sex again, you add more spermicide without removing the diaphragm.
After intercourse, the diaphragm needs to stay in place for at least six hours so the spermicide has time to neutralize any remaining sperm. However, you should not leave it in for more than 24 hours. Wearing it beyond that window without removing and washing it raises the risk of infection and toxic shock syndrome (TSS). After removal, wash it with mild soap and warm water, let it air dry, and store it in its case.
How Effective It Is
With typical use, the diaphragm has a 17% failure rate per year, according to the CDC. “Typical use” accounts for the real-world mistakes people make: inserting it incorrectly, skipping spermicide, or removing it too soon. With consistent, correct use every time, the failure rate drops, but diaphragms are still less effective than IUDs, hormonal implants, the pill, the patch, or the shot. If preventing pregnancy is your top priority, a diaphragm works best when paired with another method like condoms or withdrawal.
Benefits of Choosing a Diaphragm
The biggest draw is that it’s completely hormone-free. For people who experience mood changes, headaches, or other side effects from hormonal contraception, or who simply prefer not to use hormones, the diaphragm offers a meaningful alternative. It also doesn’t require daily action the way the pill does. You only use it when you need it, and the rest of the time it sits in a drawer.
Diaphragms are reusable. With proper care, a single device can last one to two years before it needs replacing. There’s no systemic effect on your body, and fertility returns immediately once you stop using it.
Risks and Downsides
Diaphragm use is linked to a higher rate of urinary tract infections (UTIs). The device can press against the urethra and irritate the surrounding tissue, which creates a friendlier environment for bacteria. If you’re someone who already gets frequent UTIs, a diaphragm may not be the best choice.
Some people develop irritation or an allergic reaction to spermicide, which is required every time. Irritated genital skin can also increase susceptibility to sexually transmitted infections. And unlike condoms, diaphragms offer zero STI protection, so if that’s a concern, you’ll need a barrier method in addition.
The most serious, though rare, risk is toxic shock syndrome. TSS has been documented in cases where a diaphragm was left in place for an extended period, particularly when harmful bacteria like Staphylococcus aureus are present in the vaginal tract. Removing the diaphragm within the 24-hour window and keeping it clean essentially eliminates this risk for most people.
Who Should Avoid a Diaphragm
A diaphragm may not be a good fit if you have a latex allergy (though silicone options exist), get frequent UTIs, or have a history of TSS. People with active vaginal or pelvic infections should wait until the infection clears. If you or your partner has an STI, the diaphragm won’t protect against transmission, and irritated tissue from spermicide could actually raise the risk.
The device can also be less effective after vaginal childbirth, because the shape and size of the vaginal canal may change. A refitting or switch to the one-size Caya model may help, but it’s worth discussing with a provider.
Getting a Diaphragm
In the United States, all diaphragms require a prescription. For a traditional multi-size diaphragm, that means a visit to a clinic for a pelvic exam and fitting. For the Caya, you still need a prescription, but no fitting appointment is necessary, so a telehealth visit or a quick office appointment is often enough. Spermicide is available over the counter at most pharmacies. The out-of-pocket cost for the diaphragm itself typically ranges from $0 to $75, depending on insurance coverage, and it lasts for up to two years with proper care.