Among the different contraceptive methods which are long-lasting and reversible is the contraceptive implant. Here, a thin plastic rod impregnated with progestin is placed under the skin over the medial side of the upper arm.
Progestin acts in different ways to prevent fertilization. The slow sustained release of progestin causes a negative feedback loop on the hypothalamopituitary axis which regulates gonadotropin secretion, and thereby controls the ovarian cycle. As a result, it suppresses ovulation. Another action is on the cervical mucus which becomes thick and unfavorable to spermarozoa entry, preventing fertilization. Finally, as a result of inhibition of the ovarian cycle, the menstrual cycle is arrested, and endometrial preparation for implantation does not occur, preventing successful implantation.
The contraceptive implant consists of a flexible plastic rod about 40 mm long, which contains progestin. This is released at a constant low rate into the body. It should be inserted only by a trained healthcare provider. Its action usually lasts for three years.