**1. Introduction**

In recent years, the desire for smaller families and healthy birth spacing has steadily increased in developed and developing countries alike [1, 2]. The United Nations Millennium Development Goals calls for universal access to contraceptive services so that women and couples are able to have the desired number of births at the desired time [3]. Measuring and documenting levels and trends in contraceptive use and the unmet need for family planning services is crucial to informing the decisions of healthcare providers, program planners, and those in charge of resource allocation, particularly in developing nations [4].

Available information regarding unmet needs for contraception in developing countries allows health promoters, professionals, policymakers, and funding bodies to identify the necessary level of investment required in family planning programs [5]. Women are considered to have an unmet need for contraception if they are sexually active and want to avoid becoming pregnant, but are not using any method of contraception to achieve this goal [6]. When women receive health guidance in preventing unintended pregnancies, this helps reduce unwanted births and unsafe abortions, ultimately improving both maternal and child health [7].

The ideal contraceptive method needs to be highly effective in preventing pregnancy with the minimum number of possible side-effects and risks; in addition, it should be affordable, reversible, widely available, and acceptable to people of various cultures and religions [8]. These characteristics are believed to enable better utilization of modern contraception methods by couples and, more specifically, by women, with research

showing that women transform their knowledge into behavior—in other words, that knowledge of contraceptives reduces fertility [9].

Investing in family planning is one of the most crucial measures to improve human wellbeing, as population dynamics have a fundamental influence on the pillars of sustainable development. Most importantly, the utilization of modern contraceptives is believed to be highly cost-effective in enhancing the socioeconomic status of nations and thus reducing poverty [3, 9]. This chapter gives the reader an overview of the various methods of modern contraception available, as well as their mechanisms of action, health benefits, and potential side-effects and risks, thereby allowing health care practitioners to better support women in making informed decisions about their fertility.
