Aims Reducing adolescent motherhood is an important indicator of several global health-related goals. Assessing the epidemiological burden of adolescent motherhood is important in supporting prevention initiatives to achieve these goals. Thus, the purpose of this study is to examine the trends, inequalities and determinants of adolescent motherhood in low- and middle-income countries (LMICs).

Methods We analysed 238-nationally representative demographic health surveys conducted between1990-2016 in 74 LMICs. The annual weighted prevalence of adolescent motherhood was estimated, and their trend was examined using time-series method. We estimated and compared the average annual rate of change (AARC) in adolescent motherhood. Inequalities in adolescent motherhood along different socio-demographic characteristics were described using the normalized concentration index (C) proposed by Wagstaff. A generalized estimating equation model was used to identify determinants for adolescent motherhood.

Results In total, 704,077 adolescent girls (15-19 years) were included in this study. The average weighted prevalence of adolescent motherhood was 19.46% (95%CI, 18.16%-20.75%) during 1990-2016. The prevalence varied from 7.20% to 24.90% across different regions, with the highest prevalence in Sub-Saharan Africa. Adolescent motherhood declined (AARC= -0.80%) in LMICs with some variations across regions and countries. The highest decline was observed in South & Southeast Asia (AARC= -1.79%) whereas no reduction was observed in the Latin & Caribbean region. Further, 28.10% (16/57) of the studied countries exhibited increasing in adolescent motherhood. Significant inequalities in adolescent motherhood were observed by wealth quintile (C= -0.249), level of education (C= -0.215), area of residence (C= -0.138), and exposure to media (C= -0.069). Pooled adjusted model showed that wealth quintile, employment status, media exposure, early marriage, knowledge about ovulation, partner’s greater age difference, and partner’s desire for more children are significant determinants for adolescent motherhood.

Conclusion Overall reductions in the prevalence of adolescent motherhood were observed in LMICs; however, inequalities in the prevalence persist. There was no progress in reducing the prevalence in some high burden countries. Early marriage, partner’s age difference, and their desire for more children are consistently identified as determinants for adolescent motherhood in most of the region. International policymakers could be beneficial from these findings in designing interventions to prevent adolescent motherhood.