**1. Introduction**

Contraception is the act of preventing pregnancy by interrupting the chains of events that lead to conception. It is very paramount in reducing the risk of unintended pregnancies and their attendant complications. It has been estimated that of the 210 million pregnancies that occur annually worldwide, about 80 million (38%) are unplanned, and 46 million (22%) end in abortion. Unintended unprotected intercourse is the primary cause of unwanted pregnancies, and many women with unwanted pregnancies decide to end them by abortion, which is most unsafe. Wider uptake of long-acting reversible contraceptive (LARC) methods is predicted to scale back the high rate of unintended pregnancy [1].

LARCs are defined within the UK National Institute for Health and Care Excellence guideline as contraceptive methods that need administration but once per cycle or month. Included within the category of LARCs are progestin-only contraceptive implants and other methods. Contraceptive implants are progesterone-only contraception that is inserted subdermally or within the skin. They are readily reversible with a return to fertility within days of removal. Moreover, these contraceptive devices are often safely placed within the immediate postpartum period, ensuring good contraceptive coverage [2].

In the same vein, contraceptive implants are subdermal contraception involving the delivering of a steroid progestin from polymer capsules or rods which are inserted under the skin. The hormone diffuses gradually and slowly at a stable rate, providing effective contraception within five (5) years. The safe period depends upon the precise progestin and therefore, the sort of polymer. The advantages of these implants includes the long term contraceptive action, low dose of highly effective contraception, and quick reversal to fertility after the removal of implants [3].

Furthermore, it is recorded that contraceptive implants are safe, highly effective, and long-term methods of contraception that are widely applicable to any reproductive-aged woman. Implanon is currently approved for three (3) years of use, provides excellent efficacy throughout its use, and is straightforward to insert and remove. Implants require minimal user compliance and are cost-effective. Implanon has been shown to be safe to use during lactation, may improve dysmenorrhoea (painful menstruation), and does not significantly affect bone mineral density, lipid profile, or liver enzymes. The progestin-only implants are safe options for various women including adolescents, postpartum (after birth), breastfeeding, those that are medically complicated, or those that have contraindications to or intolerance of oestrogencontaining contraceptives.

In addition, contraceptive prevalence rate is the percentage of women (15–49 years) who are in union using any type of contraception either traditional or modern. The unmet need for family planning is the ratio of women (15–49 years) not using any contraceptive methods but are either married or in a union, and who are sexually active and able to give birth to children, but do not want children again, or would really prefer to space the birth of another baby for at least two years [4, 5].

This chapter focuses on types of contraceptive implants and its mechanism of action; the side effects of contraceptive implants; health benefits and positive characteristics of contraceptive implants; those who can and cannot use contraceptive implants; reasons women are not interested in implants and factors influencing its usage.

## **1.1 Types of contraceptive implants and outline**

The historical background of the contraceptive implants shows that Norplant was the earliest implant and it had been first produced in Finland in 1983 with a 5-year lifespan. It contained six rods, each containing levonorgestrel (LNG). Continuing research centered on reducing the amount of units to facilitate easier insertion and removal led to its successor, Norplant-2 or Jadelle (two-rod implant), which was approved within the U.S**.** in 1996 but its production was discontinued globally in 2008. Implanon was launched in 1999 as one rod of etonorgestrel, with contraceptive efficacy of three (3) years. Its successor, Implanon NXT (Nexplanon), with a redesigned applicator to ease its insertion, was introduced in 2010. It is replacing Implanon in many countries. Other implants like NesteroneTM and CapronorTM, consisting of various progestins, biodegradable rods, pellets, and microcapsules remain in development. Advancement during this area has also produced male contraceptive implants MENT acetate that contains 7α-methyl-19-nortestosterone, although still undergoing approval processes [1].

In view of the above records, the following are the identified kinds of implantable contraceptives [1, 6]:

i.**Norplant:** The Norplant contraceptive implant consists of six silastic capsules, each contains 36 mg of LNG (levonorgestrel), and when inserted under the

skin, provides endless release of LNG at the rate of 30 mcg/day. It provides protection against pregnancy for 5–7 years. The associated pregnancy rate varies between 0.2 and 1.3 per 100 women-years. Its use and acceptability was hampered by the six rods with associated difficult insertion and removal, which led to its abandonment in many countries. This was discontinued in 2008 and is not any longer available for insertion.


This contraceptive is acceptable for women (14–49 years) who desire long-acting reversible contraception (LARC). It must be removed and replaced every three (3) or five (5) years. Ovulation returns within three (3) to six (6) weeks after the removal of Implanon. Implantable contraceptives provides no protection against Sexually Transmitted Infections (STIs) or Human Immunodeficiency Virus (HIV) [7].

