Introduction
There are now more adolescents globally than ever before, and the vast majority live in low-middle and middle-income countries (LMICs).1 A strong focus on their sexual and reproductive health needs will be critical to achieving several of the sustainable development goals (SDGs), including universal access to health, poverty eradication, education and gender equality.2–4 Reducing unintended adolescent childbearing has been a global priority since the 1994 International Conference on Population Development and is a target in both millennium development goals and the SDGs.5
In 2015, 19.4 million births occurred to adolescent girls (10–19 years old), of which an estimated 1–2 million were to girls under 15 years.6 7 More than 95% of adolescent births occur in LMICs.8 The number of live births per 1000 women 15–19 years old per year declined in every world region between 1990–1995 and 2010–2015, but still nearly one in five women aged 20–24 globally reported that they had initiated childbearing below the age of 20.5 9 Across all regions, sub-Saharan Africa has the highest percentage of all births occurring to adolescents (>50%)10 and the highest birth rates among adolescents—a level 200-fold higher than some countries in the Western Europe/Central Asia region.11 In most regions, adolescent births are concentrated among the poorest, most rural populations.12
Adolescent childbearing has negative consequences on the health of the mother, her neonate/child as well as on her socioeconomic well-being and educational attainment.13 The adolescent maternal mortality ratio (MMR) is one third higher than the MMR in women aged 20–24, although this increased risk is not consistent across all countries.14 15 Young adolescents (<16 years) in particular are at risk of increased maternal mortality and other negative health sequelae of childbearing.6 16 17 Most recent estimates show that maternal conditions were the leading cause of death among 15–19-year-old females18 19, and an estimated 15% of all deaths among women 10–24 years were due to maternal causes.14 Young adolescents are more likely to experience obstructed labour and fistula,7 especially very young adolescents during their first childbirth.20 In LMICs, children of adolescent mothers are at a higher risk of adverse health outcomes such as stillbirth, neonatal death, premature birth, low Apgar score and low birth weight; and the younger the mother, the greater the risk to her baby.16 20–24 At the same time, first births to women of any age are at increased risk of adverse maternal and neonatal outcomes.25 The risks associated with childbearing in adolescence are therefore compounded by the risk of first pregnancy/childbirth, and first-born children of adolescent mothers are particularly vulnerable to infant mortality and other poor child health outcomes.26 Also, there is some evidence that the risks of poor newborn outcomes of second-order and higher-order births in adolescents are higher compared with those in older women, and these effects hold after adjustment for parity and birth interval.27
Several indicators are commonly used to estimate and monitor the levels of adolescent fertility:
Age-specific fertility rate (ASFR; also called the adolescent birth rate): the number of live births per 1000 adolescents aged 15–19 per year.11The recently published Indicator and Monitoring Framework for the Global Strategy for Women’s, Children’s and Adolescents’ Health (2016–2030) proposes a modification of the adolescent birth rate to also report on young adolescents separately, so that the indicator is the adolescent birth rate (10-14, 15-19) per 1000 women in each age group, to be used as one of the Global Strategy’s 16 key indicators.28
The percentage of girls aged 15–19 years who are currently pregnant or have had a live birth,29 or, alternatively, who have ever been pregnant.30
Adolescent childbearing (also called adolescent-girl pregnancy): the percentage of women aged 20–24 (or 20–29) who had a live birth before age 15 years (early adolescent childbearing),<18 years, or<20 years.12 29 31
Median age at first birth can also capture the extent to which the initiation of childbearing affects adolescents.32
These indicators, with some variability in definitions and populations, estimate the incidence/prevalence of adolescent childbearing or timing of childbearing initiation. However, given the large adolescent global population and the specific biological and social risks to adolescent mothers and their babies, it is crucial we also understand the absolute and relative contribution of adolescent births to all births. One such indicator, used for example by the WHO European Health Information Gateway, is the percentage of all live births to mothers aged under 20 years.33 Such estimates would reflect the composition of all births in a certain population with respect to those occurring to adolescents, and thus be relevant to reproductive and maternal health programming, progress monitoring (demographic indicators, SDGs) and health service provision (midwifery and obstetrics training, clinical care provision and service organisation). This is not a measure of adolescent fertility per se as the denominator is births to women of all ages rather than the adolescent population at risk of pregnancy and would be seen as an additional indicator rather than a replacement for the existing indicators already mentioned.
The objectives of this paper are:
To propose and define a package of three indicators capturing the contribution of adolescent births to all births, and separately for first-order and second/higher-order births, and to provide data requirements for their calculation.
To calculate these indicators for adolescents from various geographical regions and describe current levels and trends over time, with a particular focus on LMICs.
To compare these indicators to other indicators of adolescent fertility to highlight their potential to understanding adolescent childbearing.