There are many options if you are looking for a safe and effective contraceptive method, and among them the IUD stands out, which has become one of the highest efficacy rates with a low incidence of side effects. However, despite the improvements it has undergone in recent decades, the IUD continues to be one of the most controversial contraceptives. Before knowing what the problems that the IUD can generate are, it is convenient that we know how it works. The IUD is a small T-shaped device that is placed inside the cervix, so that it prevents the passage of sperm. The copper IUD is for mechanical use, while the Mirena IUD includes the use of hormones that help regulate the menstrual cycle in a similar way to the contraceptive pill.

The most common problems that the IUD can cause

  • Although the IUD does not have to cause any problems unless there are serious incompatibilities (such as vaginal infections, suspicion of pregnancy, uterine cancer) there are many doubts about its use. One of the most common complaints is that after their insertion they suffer from colic that can become intense, and although they tend to disappear in a few weeks, they can be prolonged and become too significant a disadvantage.
  • Wearing the device inside the body is also one of the most common reasons for rejection. The copper IUD can cause allergies, and both it and the Mirena will lose effectiveness if they move, something that we must check regularly since another of the consequences could be that it leads to a uterine tear that leads to endometriosis.
  • Concern about whether the IUD is noticeable during sexual intercourse, and whether it can be used by any woman, is also common. This last point is where we should worry the least, since the IUD can be used by any woman even if she has not had children, contrary to common belief, and it offers greater effectiveness than most similar contraceptives.
## Clarifying anatomy and placement (important clinical note) As a practicing gynecologist, I must clarify a common point of confusion in plain-language explanations: medically, an IUD is positioned in the uterine cavity (the body of the uterus), and the insertion is done through the cervical canal. The visible strings extend through the cervix into the upper vagina to allow for self-checking and removal. Saying the device is “placed inside the cervix” can be misleading; the device sits in the uterine cavity with the arms of the T opened, and the stem passes through the internal os so strings protrude into the vagina. Why this distinction matters clinically: - Correct placement in the uterine cavity is essential for efficacy and to minimize side effects. - Misplacement (too low in the cervix or partially expelled) reduces effectiveness and increases cramping/bleeding. - The clinician must measure uterine depth (sound) before insertion and use appropriate technique for safe placement. If you ever have doubts after insertion (excessive pain, heavy bleeding, inability to feel strings), return promptly for evaluation and ultrasound if indicated. ## How IUDs work — physiology and differences between types - Copper IUDs (e.g., Paragard): The copper acts as a spermicidal agent within the uterine cavity and causes a local inflammatory reaction that impairs sperm motility and viability. It does not rely on hormones. Copper IUDs can be effective for up to 10 years depending on the model. - Levonorgestrel intrauterine systems (LNG-IUS, e.g., Mirena, Kyleena, Liletta): These release progestin locally in the uterus. They thicken cervical mucus (blocking sperm entry), thin the endometrial lining (reducing or eliminating menstrual bleeding), and can inhibit ovulation in some users. Most LNG-IUS are approved for 3–7 years depending on brand; Mirena is commonly used for up to 5 years (some approvals allow up to 8 years in certain cases—follow product labeling). Clinical implications of mechanism: - Heavy menstrual bleeding is often reduced or abolished with LNG-IUS; copper IUDs can increase bleeding and cramps initially and long-term in some users. - Systemic hormonal side effects with LNG-IUS are usually less than with systemic hormonal contraception because circulating hormone levels are low — but mood changes, acne, or breast tenderness can still occur. - The contraceptive failure rate for both types is very low (38°C (100.4°F) or chills. - Heavy bleeding soaking through pads hourly for multiple hours. - Fainting or syncope during or after insertion. - Suspected pregnancy (missed period and positive pregnancy test) or inability to feel IUD strings plus persistent symptoms. ## Resources - For product-specific pricing, accessories and supportive products, visit our [shop](/shop). - For clinical updates and detailed discussions on contraception, see [related topic](/blog). ## FAQ ### Can an IUD cause infertility? No. The IUD itself does not cause long-term infertility. Fertility typically returns rapidly after removal. The main risk to fertility associated with IUD use is pelvic infection (PID) resulting from an STI at the time of insertion; untreated PID can potentially cause tubal damage and infertility. To minimize this risk, clinicians screen for STIs in high-risk patients and follow aseptic technique during insertion. If you have concerns about future fertility, discuss them with your provider — we can tailor a plan to reduce any infection risk and monitor appropriately. ### Does an IUD increase the risk of ectopic pregnancy? An IUD reduces the overall risk of pregnancy; therefore, the absolute risk of ectopic pregnancy is lower than in non-contraceptive users. However, if a pregnancy does occur with an IUD in place, it is relatively more likely to be ectopic than a pregnancy in someone not using contraception. Any pregnancy with an IUD requires urgent evaluation (ultrasound and location assessment). If an IUD pregnancy is intrauterine and strings are visible, removal reduces miscarriage risk. If strings are not visible or ectopic pregnancy is suspected, immediate care is required. ### Is insertion more painful if you have never had children? Insertion can be more uncomfortable in nulliparous patients due to a tighter cervical canal, but many young women tolerate insertion well with brief cramping and use of pre-procedural NSAIDs. Techniques to improve comfort include: using smaller-diameter insertion instruments, offering local anesthesia (paracervical block), administering pre-procedural NSAIDs, and having the procedure performed by an experienced clinician. Misoprostol for cervical priming is sometimes used but evidence is mixed; discuss options with your provider. ### How can I tell if my IUD has been expelled or moved? - Check strings monthly for the first three months and after heavy bleeding or childbirth. - If you cannot feel the strings and have new pelvic pain or bleeding, contact your clinician immediately. - If you feel the plastic body of the IUD at the cervix or within the vagina, it may be partially expelled; do not attempt to push it back — seek clinician removal or replacement. - Ultrasound is the standard test to confirm position if expulsion or malposition is suspected. ### Can my partner feel the IUD during sex? Will it hurt them? Most partners do not feel the IUD. Occasionally, a partner may notice strings early after insertion if the strings are long or if they are felt before they soften and curl. If a partner experiences discomfort, a clinic visit can assess whether the strings need to be trimmed or the device repositioned. Rarely, strings may be trimmed too short, making them hard to feel for future checks — a balance is needed, so have this discussion with your clinician. --- If you have more specific concerns about IUD types, want help choosing between options, or need local clinic recommendations for insertion or ultrasound-guided placement, contact our clinic through the channels on this website. As with any medical decision, individualized counseling based on your health history and goals leads to the best outcomes.