A DIU, or dispositivo intrauterino, is the term used in Spanish, Portuguese, and French for an intrauterine device (IUD). It’s a small, T-shaped device placed inside the uterus to prevent pregnancy. IUDs are among the most effective forms of reversible birth control available, with failure rates below 1% per year. They come in two main types: copper and hormonal.
Copper vs. Hormonal: Two Different Approaches
The copper IUD contains no hormones at all. Instead, it releases copper ions into the uterus, which trigger an inflammatory response that creates an environment toxic to sperm. Copper concentrations in the reproductive tract become high enough that very few sperm reach the egg, and those that do are typically too damaged to fertilize it. Studies recovering eggs from copper IUD users show that embryos form at a significantly lower rate compared to non-users. A single copper IUD can prevent pregnancy for up to 10 years.
The hormonal IUD works through a different set of mechanisms. It releases a small, steady amount of a synthetic progestin directly into the uterus. This thickens the cervical mucus so sperm can’t easily enter, thins the uterine lining so a fertilized egg is less likely to implant, and impairs sperm movement and survival inside the uterus. Depending on the brand, hormonal IUDs last between 3 and 8 years.
How Effective Is an IUD?
IUDs are more effective than the pill, the patch, condoms, and most other reversible methods. With typical, real-world use, the copper IUD has a first-year failure rate of 0.8%, meaning fewer than 1 in 100 women will become pregnant. The hormonal version is even more effective at 0.2%. For comparison, the pill fails about 8% of the time with typical use, and male condoms fail about 15%. The only methods that rival IUDs in effectiveness are the implant (0.05% failure rate) and sterilization.
People also tend to stick with IUDs longer than other methods. About 78% of copper IUD users and 80% of hormonal IUD users are still using the device after one year, compared to 68% for the pill.
What the Insertion Feels Like
Getting an IUD placed takes only a few minutes in a clinic. After confirming you’re not pregnant, a clinician uses a speculum to visualize the cervix, cleans the area, then measures the depth of the uterus (typically 6 to 9 cm) before sliding the device into place through the cervical opening. Thin strings are trimmed to about 3 to 4 cm so the device can be checked and eventually removed.
The insertion itself is acutely painful for many people, particularly those who haven’t been pregnant before. This is actually one of the main reasons some people avoid IUDs in favor of less effective methods. Pain relief options like local anesthetics or numbing gels can help. Cramping and discomfort similar to period pain are common for a few days afterward. A follow-up visit is typically scheduled 4 to 6 weeks later to confirm the device is still in the right position.
Side Effects to Expect
The two types of IUDs affect your period in opposite ways. The copper IUD often makes periods heavier, longer, and more painful, especially in the first few months. Some spotting between periods is also common early on. These changes usually improve over time but don’t always disappear entirely. Because the copper IUD is hormone-free, it doesn’t carry the risks associated with hormonal contraception, such as blood clots.
The hormonal IUD tends to make periods lighter. Many users eventually have very light periods or stop getting them altogether. Some people experience hormonal side effects like headaches, breast tenderness, or mood changes, though these are generally milder than with the pill because the hormone acts mostly within the uterus rather than circulating through the entire body.
Who Shouldn’t Use One
Most people can safely use an IUD, but there are exceptions. The CDC’s medical eligibility guidelines identify certain conditions where IUD use poses unacceptable health risks. These include active pelvic infections, certain uterine abnormalities, and unexplained vaginal bleeding that hasn’t been evaluated. For the hormonal version specifically, some hormone-sensitive conditions may be a concern. The uterus also needs to measure at least 6 cm deep for the device to be placed safely.
Fertility After Removal
One of the biggest advantages of an IUD is that fertility returns quickly once the device is removed. Unlike some hormonal methods that can delay ovulation for months, IUDs have no lasting effect on your ability to get pregnant. In studies tracking women who had their IUD removed specifically to conceive, over half became pregnant within the first three months. The device does not cause long-term changes to the uterus or reproductive system.