A diaphragm is a shallow, dome-shaped cup made of silicone that you insert into your vagina to cover your cervix before sex. It works as a physical barrier, blocking sperm from reaching an egg. Diaphragms are reusable, hormone-free, and require a prescription in the United States. When used correctly with spermicide, they’re about 92 to 96 percent effective at preventing pregnancy.
How a Diaphragm Works
The diaphragm sits snugly over your cervix, the narrow opening at the bottom of your uterus. During sex, it physically prevents sperm from passing through the cervix and into the uterus where fertilization happens. You use it together with spermicide, a gel or cream that kills or immobilizes sperm on contact. The spermicide goes inside the cup and around the rim before insertion, creating both a physical and chemical barrier.
A diaphragm doesn’t release hormones, which makes it appealing if you want to avoid side effects like mood changes, weight fluctuations, or cycle disruption that can come with hormonal birth control. You only use it when you need it, so there’s nothing to take daily or have implanted.
Effectiveness Rates
With perfect use, meaning you insert it correctly every single time and always pair it with spermicide, diaphragms prevent pregnancy about 92 to 96 percent of the time. In real-world use, where mistakes happen, that number drops to around 83 percent. That means roughly 17 out of 100 people using a diaphragm as their only method will get pregnant in a typical year.
For comparison, condoms have a typical-use failure rate of about 13 percent, and hormonal IUDs sit under 1 percent. Diaphragms are most effective when you’re consistent about using spermicide, leave the device in for the right amount of time after sex, and check the fit periodically.
Types and Sizing
The most widely available diaphragm in the U.S. is the Caya, a one-size-fits-most option that doesn’t require a fitting appointment. It’s designed with a contoured shape and a grip for easier removal. Traditional diaphragms come in multiple sizes, ranging roughly from 60 to 90 millimeters in diameter, and require a healthcare provider to measure your cervix and determine the right fit.
Proper fit matters. A diaphragm that’s too small can shift out of place during sex, and one that’s too large can feel uncomfortable or not seal properly against the vaginal walls. If you’ve given birth, gained or lost more than about 15 pounds, or had pelvic surgery, you may need to be refitted.
How to Insert and Remove It
Before inserting, apply about a tablespoon of spermicide to the inside of the cup and spread a thin layer around the rim. Fold the diaphragm in half, find a comfortable position (standing with one foot elevated, squatting, or lying down), and slide it into your vagina, pushing it up and back until it covers your cervix. You should be able to feel your cervix through the silicone, like a firm, rounded bump similar to the tip of your nose.
You can insert the diaphragm up to two hours before sex. If more than two hours pass before intercourse, or if you have sex again while the diaphragm is still in, add more spermicide without removing the device. After sex, leave it in place for at least six hours so the spermicide has time to neutralize any remaining sperm. Don’t leave it in for more than 24 hours total.
To remove it, hook a finger under the rim or grip and pull it down and out. Wash it with mild soap and warm water, let it air dry, and store it in its case.
Benefits of Using a Diaphragm
- No hormones. It won’t affect your menstrual cycle, mood, or other systems the way pills, patches, or hormonal IUDs can.
- Use only when needed. Unlike daily pills or long-acting devices, you only deal with it around the time you have sex.
- Reusable. A single diaphragm lasts one to two years with proper care, making it relatively inexpensive over time.
- You control it. You insert and remove it yourself, and your partner doesn’t need to be involved in the process.
- No waiting period to get pregnant. Fertility returns immediately once you stop using it.
Drawbacks and Limitations
Diaphragms don’t protect against sexually transmitted infections. If STI prevention matters, you’ll still need condoms. Some people find insertion awkward at first, though most get comfortable with practice after a few tries.
Spermicide can cause irritation for some people, particularly with frequent use. The most common spermicide ingredient, nonoxynol-9, can irritate vaginal tissue and may actually increase susceptibility to STIs if used multiple times a day. If you notice burning or discomfort, talk to a provider about alternative spermicide options.
Diaphragm use is linked to a slightly higher risk of urinary tract infections. The rim of the device can press against the urethra, making it harder for your bladder to empty completely, which creates an environment where bacteria are more likely to grow. Urinating after sex and ensuring proper fit can help reduce this risk.
You also can’t use a diaphragm during your period or if you have a vaginal infection, and some people with certain anatomical differences may not be good candidates for one.
Getting a Diaphragm
In the U.S., you need a prescription. Some providers will prescribe the Caya without an in-office fitting since it’s designed as one size. For traditional sized diaphragms, you’ll need a pelvic exam so the provider can measure your cervix and find the right diameter. Many insurance plans cover diaphragms under preventive care provisions, and without insurance, the device itself typically costs between $0 and $75, plus the ongoing cost of spermicide.
Once you have one, check it regularly for holes or weak spots by holding it up to the light or filling it with water. Even a small tear means it’s time for a replacement. With daily care and proper storage away from heat, a well-maintained diaphragm reliably lasts one to two years before the silicone starts to degrade.