Implants - How they work
Implants contain a single hormone progesterone. This hormone influences the way the ovary functions by interfering with egg formation. Because the hormone is constantly being released into the body, this effect lasts as long as the implant is present. It is also thought that the hormone has an effect on the lining of the uterus by making it thin and therefore unfavourable for implantation. This influence on the uterus causes a change in the menstrual cycle with scanty irregular menses or no menstrual flow.
Attribution: Avallain