The coil explained: IUD and IUS

The coil is small, sits inside the womb, and is one of the most effective forms of contraception there is: over 99 percent, and once it is in you can forget about it for years. There are two families, and they work in different ways.

The copper coil (IUD)

The copper coil has no hormones. The copper changes the fluid in the womb so that sperm cannot fertilise an egg. It works the moment it is fitted, lasts 5 to 10 years depending on the type, and is the most effective emergency contraception there is if fitted within 5 days. Because there are no hormones, your natural cycle carries on. Some people find their periods are heavier or crampier, especially in the first few months.

The hormonal coil (IUS), including the Mirena

The hormonal coil releases a small amount of a progestogen (levonorgestrel) into the womb. It thins the womb lining and thickens the mucus at the neck of the womb. Most people find their periods become much lighter, and many stop having them altogether, which is often welcome. The Mirena lasts up to 8 years for contraception; smaller versions (such as Kyleena and Jaydess) last 5 and 3 years.

Fit and forget, and fully reversible

Both are put in during a short appointment and removed whenever you choose. Your fertility returns straight away after removal. Nothing to remember day to day, nothing to take, no oestrogen.

The hormonal coil also does far more than prevent pregnancy. More on that in a separate piece.

Coming soon. We are extending our clinic so that a doctor can fit coils for you, including the Mirena. It is not bookable yet. For now, coils are fitted free on the NHS at GP surgeries and sexual health clinics. Our women's health lead, Dr Ferhat Uddin, will fit them.