High fertility translates into faster population growth, with a disproportionate share of the population aged 15 or younger. High fertility rates pose challenges for governments struggling to meet the demand for education and health services, and to sustain development gains.

In high-fertility countries, economic, social, institutional and geographic barriers may prevent women from accessing quality family planning information and supplies. Barriers may be particularly insurmountable for young people. Together, these barriers stop millions of people from exercising their reproductive rights.

Women with at least a secondary education prefer to have fewer children compared to women with little or no education. Educated women are also in a better position to break the barriers to decent, paid employment later in life.

The countries where a woman has an average of three to four children are geographically and economically diverse and have followed different paths at different paces as their fertility rates declined.

A total fertility rate of three or four may mask large differences within countries, with wealthier people in urban areas having access to contraception, while rural, ethnic minorities have limited access to family planning programmes. Adolescents in some of these countries also have limited access to contraception information and services, resulting in comparatively higher rates of teenage pregnancy.

In some countries where fertility has been steadily declining, economic shocks, wars and other crises can cause fertility rates to dip suddenly as couples choose to delay having children and then rebound after the crisis, when stability and security return.

Countries where fertility rates have been low for many years are generally more developed. Basic reproductive and other rights are mostly met. Challenges facing these countries typically include an increasing share of older people in their populations and higher associated health-care costs, as well as a shrinking labour force.

Current fertility rates of these countries indicate that women have become more effective in preventing pregnancies and spacing births. Where education and career are high priorities, marriage and childbearing may take a back seat. Women who opt to delay pregnancy until their late 30s or 40s are at greater risk of infertility and complications during pregnancy.

Long-standing gaps in support for balancing work and family life can inhibit women from having the number of children they want to have. Challenges that women in low-fertility countries face in exercising their reproductive rights include economic hardship, a lack of affordable housing, high childcare costs, and uncertain labour markets.