The contraceptive implant: fitting, side effects and what to expect

The implant is a matchstick-sized plastic rod that a doctor or nurse puts under the skin of your arm. It releases the hormone progestogen, which stops the ovaries releasing an egg each month.

The NHS says it is over 99% effective when replaced every 5 years, with fewer than 1 in 100 users becoming pregnant in a year. Effectiveness drops if it is not replaced on time. It does not protect against sexually transmitted infections, so condoms remain advisable.

Insertion takes minutes. A healthcare professional uses a local anaesthetic injection or spray, makes a small cut in the skin of the upper arm, places the implant under the surface and seals the wound with a dressing.

If it is fitted within the first 5 days of your period, protection is immediate; later than that, use another method for 7 days. After a birth, fitting before day 21 gives immediate protection; after a miscarriage or abortion, fitting within 5 days does.

Removal mirrors fitting: local anaesthetic, a small incision, the device taken out and a dressing applied. Doctors, nurses and young people's service staff do both, and you do not need to go back to the original provider. It can be removed at any time.

Your chance of getting pregnant returns to what it was before straight away, so if you do not want a pregnancy, start another method as soon as it comes out.

The NHS says the implant is not suitable if you have a history of cardiovascular disease such as stroke, a liver condition such as cirrhosis, breast cancer or unexplained vaginal bleeding.

Some medicines reduce its effectiveness and need a professional's advice: TB medicines, epilepsy medicines, HIV medicines and the antifungal griseofulvin, along with the herbal remedy St John's wort.

It is very common to have a change in your periods. They may be lighter, irregular, heavier or more painful, longer, or stop completely, and they can become unpredictable. Other reported effects include headache, sore breasts, weight gain, acne, and thrush or bacterial vaginosis, but the NHS says there is not enough evidence to say whether the implant causes them.

Contact a GP or sexual health clinic if period changes become a problem.

Rarer complications include blood clots, ectopic pregnancy if the implant fails, infection at the insertion site with swelling and pain, and movement of the implant, usually by a few centimetres from where it was placed. Seek care if you suspect infection or that it has moved.

The implant is safe to use while breastfeeding and does not affect your baby or milk supply. Doctors, nurses or young people's service staff do the fitting.