This report examines trends in adolescent childbearing using techniques that focus on the most vulnerable girls, such as child mothers, girls with repeat adolescent childbearing, and births that occur in dangerously quick succession. In using these new measures, it uncovers the untold story of more than 50 years of adolescent childbearing in the world’s low- and middle-income countries.

The new measures reveal that the issue is not just about whether or not a girl gives birth in adolescence but if, when and how many births she experiences. That is, adolescent childbearing comprises three fundamental and interconnected fertility processes: (i) the timing of a first adolescent birth, (ii) the spacing between adolescent births and (iii) the quantity or total number of births to each adolescent mother.

This multifaceted process is most immediately shaped by factors such as the age of menarche and sexual debut, the frequency of sexual activity, the patterns of marriage and union formation, and the use and effectiveness of contraception. It is worth emphasizing that the majority of first births to girls aged 17 years and younger, in 54 developing countries with data, occur within marriage or cohabiting unions. More distal determinants – such as girls’ education – are also critical to the process and include gendered social, economic, cognitive and psychological factors at the individual, peer, family and community levels.

Additionally, broader norms, values, inequalities, events, economic forces, and national laws, policies and priorities shape the adolescent fertility landscape.