IUDs affect sperm movement to the egg and change the lining of the uterus (womb) to make it difficult for a fertilised egg to take hold. A fertilised egg is when a sperm and egg have merged together. 

Hormonal IUDs thicken the mucus at the neck of the uterus (womb), blocking the sperm. They may also affect ovulation by changing the hormones that cause an egg to be released each month. 

Copper IUDs affect the way sperm can move and survive in the uterus, and stop sperm cells from reaching & fertilising the egg. IUDs also change the lining of the uterus to stop a fertilised egg from sticking.

There are a number of differences between the copper and hormonal IUD:

IUDs are suitable for most people. A doctor will assess you to see if it’s suitable for you. The hormonal IUD is the most popular form of long acting reversible contraception (LARC) in the world. It is safe for people who have never had a pregnancy to have an IUD. 

An IUD might not be right for you if you: 

• have an active pelvic infection or abnormal vaginal bleeding
• are at high risk of STIs i.e. you have multiple partners & don’t use a condom
• have had certain types of surgery to the cervix
• have a condition that might alter the shape of the uterus such as fibroids
• have had breast cancer in the last five years (hormonal IUD only)
• have heavy painful periods or if you are anaemic (copper IUD only)

• Over 99% effective at preventing pregnancy 
• Last between five and ten years
• Once it has been inserted, you only need to check the strings monthly 
• A rapid return to usual fertility (ability to have a baby) once the IUD is removed 
• A hormonal IUD may help with heavy periods and period pain 
• Does not interfere with breastfeeding 
• Safe for people who have never had a pregnancy to have an IUD 
• The device can be removed at any time by a trained doctor or nurse

• A small risk of infection at the time the IUD is fitted and for the first three weeks (1 in 300 people)
• A small risk of perforation, which is when the IUD makes a hole in the wall of the uterus when it is fitted (1 in 500 people)
• If the IUD does not work and you get pregnant, there may be complications if you continue with the pregnancy
• A small risk that the IUD can fall out 

Even if an IUD becomes infected or perforates, fertility is rarely affected.

Hormonal IUD side effects 

Hormonal side effects are rare but may cause headaches, acne, breast tenderness and increased appetite in the first few months. You are more likely to develop ovarian cysts with a hormonal IUD. Most ovarian cysts are harmless and disappear without treatment in two to three months.

• IUDs are inserted using a small procedure carried out by a trained professional in a clinic. Most people feel some cramping or pain when they have an IUD inserted but it usually only lasts a couple of minutes. For a small number of people, the pain is more severe. Some people feel dizzy and there is a small chance of fainting. Your doctor will discuss pain relief with you.
• Never attempt to remove an IUD yourself. Removal should only be undertaken by a health professional, who will remove it by pulling gently on the threads  Mild cramping and some bleeding may be experienced when the IUD is removed. 
• It is important to consider contraception before your IUD is removed as your fertility will return to normal as soon as it is removed.  
• Hormonal IUDs can be inserted at any time if there is no chance you are pregnant. They take seven days to start working as a contraceptive
• Copper IUDs can also be inserted at any time as long as you are not pregnant. They start working as soon as they are inserted.
• For most people, it is safe to have an IUD fitted four weeks after having a baby.

Most people feel some cramping or pain when they have an IUD inserted but it usually only lasts a couple of minutes. For a small number of people, the pain is more severe. Some people feel dizzy and there is a small chance of fainting. Your doctor will discuss pain relief with you.

This video below from Sexual Health Victoria helps explain more about pain and IUDs.

An IUD can be inserted at Family Planning Tasmania clinics, some GPs, private gynaecologists and public hospitals. 

At Family Planning Tasmania, an IUD insertion involves two or three appointments:

1. Assessment: discuss the procedure, check your suitability, arrange any necessary tests. 
2. Insertion: a doctor inserts the IUD.
3. Follow up: your doctor may ask you to return for a check six weeks after the insertion.