Two devices, two logics
| Copper IUD | Hormonal IUD | |
|---|---|---|
| Principle | Copper ions make the uterine environment toxic to sperm and prevent fertilisation | A locally released progestogen thickens mucus and thins the uterine lining |
| Hormones | None | Yes, but mainly local and at a very low dose |
| Effect on periods | Often heavier and more painful, especially in the first months | Often lighter, and absent after a year for many users |
| Duration | 5 to 10 years depending on the model | 3 to 8 years depending on the model |
| Other use | The most effective emergency contraception, fittable up to five days after intercourse | Treatment for heavy periods |
Authorised durations vary from country to country and have changed recently for several models: check locally rather than assume.
Effectiveness
From 0.1 to 0.8 pregnancies per 100 women per year depending on the device, in perfect and typical use alike — since there is nothing to do day to day. With the implant, these are the most effective reversible methods.
Insertion
- It is done in a consultation and takes a few minutes. The device is introduced folded inside a fine tube, through the cervix.
- Pain is real and highly variable: from discomfort to sharp pain. Long minimised, it is now the subject of explicit guidance — local anaesthetic to the cervix, analgesia beforehand, information in advance. Ask for this before the appointment; it is hard to refuse once requested.
- Cramps and bleeding for a few days are usual.
- A thread protrudes from the cervix and can be checked yourself. It is not felt during sex in most cases.
The risks, in order of frequency
- Expulsion: uncommon, and most likely in the three months after fitting (NHS, 2024). Hence the value of checking the threads.
- Uterine perforation: rare, and more likely when the device is fitted soon after childbirth or during breastfeeding (CDC, 2024).
- Infection: the added risk is limited to the first three weeks after insertion and remains small. The IUD itself does not expose you to infection.
- Ectopic pregnancy: the IUD makes it less likely overall, because it makes any pregnancy unlikely. But if pregnancy does occur with an IUD in place, the proportion that are ectopic is higher — hence the rule: a positive test with an IUD means being seen quickly.
Three myths to discard
"Not before you have had a child." False: insertion is possible in a woman who has never given birth, and is recommended by professional bodies. "It causes infertility." False: fertility returns as soon as it is removed, with no delay. "It works by ending a pregnancy already started." No: it acts on sperm and on fertilisation.
When to seek advice
Persistent pelvic pain, fever, foul-smelling discharge, threads you cannot find or a device you can feel at the cervix, unusual bleeding, a positive pregnancy test. The IUD gives no protection against sexually transmitted infections.