How does the implant work

The contraceptive implant is a flexible rod the size of a matchstick that sits just under the skin of your arm. 

It contains a small amount of etonogestrel, a synthetic progestogen. This is released at a controlled rate for 3 years to prevent pregnancy.

This hormone is absorbed into your bloodstream. It can affect many of your body’s organs, but the effects that make it an excellent contraceptive are:

  • it stops you from producing an egg (ovulating) – no egg means there’s nothing to fertilise

  • it thickens the cervical mucus so the sperm cannot reach the womb

  • it thins the womb lining so a fertilised egg cannot implant, but most people will not produce an egg at all

How the implant affects the body

The hormones from the implant travel all over the body in the bloodstream (as do the hormones in a pill), with positive and negative effects. The implant:

  • stops the pituitary gland in the brain from starting ovulation, so no egg is released

  • thickens the cervical mucus so sperm cannot get through

  • thins the womb lining, so an egg can’t implant

  • reduces the risk of cancer of the womb lining

  • reduces the risk of cancer of the ovary

How the implant affects your ovaries and womb (uterus)

Around the time of ovulation, the fluid that’s produced by your cervix (known as cervical mucus) gets slippery, making it easier for sperm to enter the womb. At the same time, the lining of the womb gets thicker so it’s easier for an egg to implant.

The hormones from the implant cause changes in the womb and ovaries. No egg is released, the cervical mucus is thicker and the womb lining is thinner.

How long does it last?

The implant will be effective contraception for 3 years. Over time, the hormone does get released at a slower rate, but the levels stay high enough for it to work well the whole time.

Types of contraceptive implants

At the moment, there’s only 1 brand of contraceptive implant available in the UK. It’s called Nexplanon and it uses a type of progestogen called etonogestrel.

When will it stop you from getting pregnant? 

If you get the contraceptive implant inserted during the first 5 days of your period, you’re protected immediately.

If you start it at any other time, you’ll need to use extra contraception, such as condoms, for the first 7 days. After that, you’ll be covered.

Learn more about getting the implant fitted.

Everything you wanted to know about sexual health and wellbeing - your questions answered by our expert team.