**1.2 The mechanism of action of contraceptive implants**

The progestin-containing implantable contraceptives inhibit ovulation and restrict sperm penetration through sticky cervical mucus. This is done as a result of the antiestrogenic actions of the progestins, which affect the cervical mucus by making it sticky or glutinous, scanty, and impassable to sperm therefore preventing or hindering fertilisation of the ovum. High doses of progestins also prevent gonadotropin secretion, thereby halting the maturation of the follicles and ovulation. This double effect allows the efficacy and effectiveness of implantable contraceptives to be maintained though ovulation is not consistently altered in etonorgestrel implantable contraceptive users towards the end of the 3-year period of use. Oocytes are not fertilised even if the follicles grow while using progestin implantable contraceptives. Even if the follicle ruptures, the abnormalities of the ovulatory cycle or phases prevent the release of a viable ovum or egg. Although progestin suppresses endometrial activity, this is often not a contraceptively significant effect since the most mechanisms of action prevent fertilisation. There has never been any signs of embryonic development found among contraceptive implant users, showing that progestin implants are not medication or substances that cause pregnancy to terminate prematurely. Implants are simpler, easier and safer to use than other contraceptive methods because they do not require regular action by the user [8].
