Praise be to Allah.
There is nothing wrong with using this method of contraception, which is based on placing a device into the lower forearm which secretes a hormone that increases the thickness of mucus around the cervix of the womb, thereby preventing sperm from reaching and fertilising the egg.
On the website Majallat Hayya it says: We regard this device as being 99% effective in preventing pregnancy, if it is used and implanted correctly. The way in which this device works to prevent pregnancy after being implanted is by releasing the hormone progestogen, which is an alternative to the progesterone that naturally occurs in the blood. It suppresses the monthly production of eggs and increases the thickness of mucus around the cervix of the womb, and prevents sperm from reaching the egg.
The second way in which this hormone works is by weakening the lining of the womb, making it unable to support the fertilised egg. End quote.
This method is not free of side-effects, such as disruption of the menstrual cycle. Some women may suffer from intermittent bleeding that goes on for a long time.
If a woman needs to use contraception for a while, she should consult specialists who are trustworthy in terms of their knowledge and experience, and who understand her situation and her general state of health.
After that, she should look into the effects of this implant; if the harm it may cause is less than the benefit of using it, then there is nothing wrong with using it in that case.
For more information, please see the answer to question no. 174279.
And Allah knows best.