A woman’s diaphragm is a small, shallow cup made of silicone that sits inside the vagina and covers the cervix to prevent pregnancy. It’s a non-hormonal, reusable form of birth control that works by physically blocking sperm from reaching the uterus. Used with spermicide, it’s one of the oldest barrier methods still available, and it remains a practical option for people who want contraception they control and only use when they need it.
How a Diaphragm Works
The diaphragm prevents pregnancy in two ways. First, the dome-shaped cup creates a physical seal over the cervix, the narrow opening between the vagina and uterus, so sperm can’t pass through. Second, spermicide gel applied to the inside of the cup before insertion kills sperm on contact. Neither mechanism involves hormones, which is one of the main reasons people choose it over pills, patches, or hormonal IUDs.
You insert the diaphragm before sex and must leave it in place for at least six hours afterward to ensure the spermicide has time to neutralize any remaining sperm. It should not stay in for more than 24 hours total, as prolonged wear raises the risk of irritation or infection. If you have sex more than once while wearing it, you’ll need to add more spermicide each time without removing the diaphragm.
Effectiveness Rates
With perfect use, the diaphragm has a failure rate around 4%, meaning about 4 out of 100 people using it exactly as directed will become pregnant in a year. In typical use, which accounts for real-world mistakes like inconsistent spermicide application or incorrect placement, the failure rate climbs to roughly 17%. That puts it in a similar range to other methods you use at the time of sex, like the sponge or withdrawal, which have typical-use failure rates between 14% and 27%.
The gap between perfect and typical use is worth paying attention to. Effectiveness depends heavily on inserting the diaphragm correctly every time, using enough spermicide, and leaving it in long enough afterward. People who are comfortable with their anatomy and consistent with the routine tend to get results closer to the perfect-use number.
Traditional vs. Modern Designs
For decades, diaphragms came in multiple sizes and required a pelvic exam so a provider could determine the right fit. Traditional models used a latex dome with a metal spring rim, and the fitting process was one of the barriers that made them less convenient than other options.
The Caya contoured diaphragm, which entered the U.S. market as the first new design in over 50 years, changed that. It uses a silicone cup with a nylon spring and a contoured shape designed to fit most women without individual sizing. Clinical studies confirmed the single-size design works for the majority of people who could wear a traditional diaphragm. It also includes a removal dome that makes it easier to take out, a feature specifically developed through user testing with new users. Some providers can prescribe the Caya without a fitting exam, which simplifies access considerably.
That said, diaphragms are the wrong shape for roughly 1 in 7 women, regardless of the model. Anatomical differences in vaginal or cervical position can make it difficult for the device to form a reliable seal.
Getting a Prescription
You need a prescription to buy a diaphragm. If you’re getting a traditional sized model, a provider will perform an internal vaginal exam to determine the correct size. With the Caya, some providers skip the fitting exam, though they may still want to confirm it sits properly.
Annual checkups are recommended to verify the fit hasn’t changed. Weight fluctuations and childbirth can alter vaginal shape enough that a diaphragm no longer covers the cervix effectively. If either of those happens, you should get refitted before relying on your current device. A single diaphragm typically lasts one to two years with proper care, and if you notice any damage like cracks or holes, you’ll need a new prescription.
Who Should Avoid a Diaphragm
Certain anatomical conditions make a diaphragm unreliable or uncomfortable. These include uterine prolapse (when the uterus drops lower into the vaginal canal), a large cystocele or rectocele (when the bladder or rectum bulges into the vaginal wall), and a history of recurrent urinary tract infections. Because the rim of the diaphragm presses against the vaginal walls near the urethra, it can contribute to UTIs in people already prone to them.
People with a sensitivity to silicone, latex (in older models), or the chemicals in spermicide should also consider alternatives. Skin irritation from spermicide can affect both you and a sexual partner.
Benefits and Risks
The biggest practical advantage is that a diaphragm is hormone-free and only used when you need it. There’s nothing to take daily, no device implanted in your body, and no systemic side effects like mood changes or weight fluctuations that some people experience with hormonal methods. You can insert it up to two hours before sex, so it doesn’t have to interrupt the moment. It’s also reusable, which makes it relatively inexpensive over time compared to monthly prescriptions.
Serious side effects are rare. The most common issue is an increased risk of urinary tract infections, likely caused by the rim pressing on the urethra and making it easier for bacteria to enter. Toxic shock syndrome is a theoretical risk with any device left in the vagina, but it’s extremely uncommon with diaphragm use. Some people find the spermicide irritating, which can cause redness or discomfort in the vaginal lining.
Care and Maintenance
After each use, wash the diaphragm with mild soap and warm water, then let it air dry completely before storing it in its case. Avoid using oil-based lubricants or medications (like certain vaginal creams) with it, as these can degrade the silicone over time. Before each use, hold it up to light and check for thin spots, holes, or cracks. Even a tiny imperfection can compromise the barrier, so replace it if you see any damage. With consistent care, one diaphragm should last one to two years before it needs replacing.