What are the side effects of getting an IUD?

Patient's question:

What are the side effects after getting an IUD, and does it have anything to do with age? If I take it out after wearing it for a long time (around 3~5 years), will it affect fertility? Is it still possible to get pregnant unexpectedly after getting an IUD? Please explain in detail for those who are informed. Thank you

Doctor's answer:

The use of an intrauterine device (IUD) can have certain side effects, with the five most common side effects after insertion.
Bleeding: 3-4 days after insertion, most women may experience light bleeding. This usually does not require treatment and resolves on its own within a week.
Increased menstrual flow: In the initial stages of using an IUD, especially during the first three months, some women may experience varying degrees of increased menstrual flow, prolonged periods, or irregular spotting. This typically improves naturally after three months. If the menstrual flow increases by 1-2 times compared to before insertion, or if irregular bleeding persists for an extended period, it may indicate anemia, and medical attention should be sought promptly.
Lower abdominal pain or backache: After insertion, a small number of women may experience mild lower abdominal pain or backache. These symptoms usually disappear on their own after a short adaptation period.