The copper IUD does not cause infertility. This is one of the most persistent concerns about the device, but decades of research consistently show that fertility returns quickly after removal and that long-term use does not damage your reproductive system. The confusion largely traces back to a poorly designed IUD from the 1970s that did cause serious problems, but modern copper IUDs are fundamentally different devices.
How the Copper IUD Actually Works
The copper IUD prevents pregnancy primarily by impairing fertilization rather than by affecting your hormones or ovulation cycle. Copper ions released by the device accumulate throughout the reproductive tract, including the fallopian tubes, where they are toxic to sperm. The copper reduces sperm motility, viability, and ability to fertilize an egg. It also affects oocytes (eggs) before fertilization can occur.
Importantly, the copper IUD has no effect on follicular development or ovulation. Your body continues its normal hormonal cycle the entire time the device is in place. There is also evidence that copper alters the uterine lining in ways that reduce receptivity to a fertilized egg, providing a secondary layer of protection. But none of these mechanisms cause permanent changes. Once the device is removed, the copper clears from the reproductive tract and these effects stop.
Pregnancy Rates After Removal
Studies tracking women after IUD removal show conception rates that match or even exceed those of women using other contraceptive methods. In one prospective study, 81% of former IUD users became pregnant within 12 months of removal, compared to 70% of women who had been using non-IUD contraception. That difference was not statistically significant, meaning the IUD group was not at any disadvantage.
Among women who had never been pregnant before (a group that might be especially concerned about future fertility), IUD users actually had higher 12-month pregnancy rates than non-IUD users: 92% versus 61%. While this doesn’t mean IUDs boost fertility, it clearly shows they don’t harm it. The duration of IUD use also made no difference. Women who used the device for many years conceived at the same rate as those who used it briefly.
The Dalkon Shield Problem
Much of the fear linking IUDs to infertility comes from the Dalkon Shield, a device introduced in the 1960s. The Dalkon Shield had a tail made of twisted strings that acted like a wick, allowing bacteria to migrate upward from the vagina into the uterus and fallopian tubes. This design flaw caused widespread pelvic inflammatory disease (PID), infected pregnancies, miscarriages, and lasting reproductive damage. Thousands of lawsuits followed, and the device was pulled from the market.
Modern IUDs use monofilament strings that do not harbor bacteria the same way. Federal regulations now require all medical devices, including IUDs, to be tested for safety before reaching the market. The copper IUD available today (ParaGard in the U.S.) bears little resemblance to the Dalkon Shield beyond being placed in the uterus.
Copper IUDs and Blocked Fallopian Tubes
Tubal occlusion, where the fallopian tubes become blocked or scarred, is one of the leading causes of infertility. A study published in the New England Journal of Medicine specifically investigated whether copper IUD use increased this risk among women who had never been pregnant. The answer was clear: the odds ratio for tubal occlusion associated with previous copper IUD use was 1.0, meaning no increased risk whatsoever.
The study also found that the duration of IUD use, the reason for removal, and whether the user experienced any gynecologic problems while using it made no difference to tubal infertility risk. What did increase the risk of blocked tubes was infection with Chlamydia trachomatis, a sexually transmitted infection. This distinction matters because it points to infections, not the device itself, as the real threat to tubal fertility.
The Real Risk Factor: Untreated Infections
The connection between IUDs and infertility that does hold up in the research is indirect. Any pelvic infection, whether or not an IUD is present, can scar the fallopian tubes and impair fertility if left untreated. With modern copper IUDs, there is a small, temporary bump in infection risk in the first 20 days after insertion. During this brief window, bacteria can potentially be introduced during the insertion procedure itself. After that initial period, the infection risk returns to baseline.
Sexually transmitted infections are the primary concern. A prospective cohort study found that past infection with Mycoplasma genitalium (a lesser-known STI) was associated with longer time to conception, with only 68% of previously infected women conceiving within 12 months compared to 80% of those without past infection. This effect was tied to the infection history, not to IUD use.
This is why screening for STIs is recommended before or at the time of IUD insertion. If you have an existing infection, it can be treated. The IUD itself is not the source of infection, but having any foreign body in the uterus during an active, untreated pelvic infection can potentially worsen outcomes.
Ectopic Pregnancy Risk
One concern you may encounter is ectopic pregnancy, where a fertilized egg implants outside the uterus, typically in a fallopian tube. If you become pregnant while using a copper IUD (which is rare, given its over 99% effectiveness), the risk of that pregnancy being ectopic is higher than normal. However, because the IUD prevents the vast majority of pregnancies from happening at all, your overall absolute risk of ectopic pregnancy is actually lower than that of a sexually active person using no contraception. An ectopic pregnancy can damage a fallopian tube if not treated promptly, but this scenario is uncommon with a properly placed copper IUD.
What This Means for Your Decision
If you’re considering a copper IUD and planning to have children later, the evidence is reassuring. The device does not affect ovulation, does not cause tubal damage, and fertility returns quickly after removal. The historical association between IUDs and infertility is a legacy of a flawed 1970s product that no longer exists on the market. The most important thing you can do to protect your fertility while using any IUD is to get screened for sexually transmitted infections and seek treatment promptly if you develop symptoms of a pelvic infection, such as unusual discharge, pelvic pain, or fever.