Ecological analysis of adolescent birth rates in Brazil: Association with Human Development Index.

Background: Adolescent pregnancy is a multidimensional public health problem. It is known that every year in Brazil approximately 1.1 million adolescents become pregnant and around 20% of all newborns are born to teenage mothers.

Aim: This ecological study describes the spatio-temporal patterns of the percentages of live births to adolescent mothers between the years of 2010 and 2016 in Brazil and their associations with human development indexes in the meso-regions where they reside.

Methods: Percentages of live births to adolescent mothers are the ratio between the number of live births to women aged 10-19 years old and total number of live births in each Brazilian meso-regions during the study period. A spatio-temporal Bayesian model was used to associate the percentages of live births to adolescent mothers with the human development index of each meso-region. Moran's index was used to measure the spatial autocorrelation between the meso-regions at an aggregate level, whereas the local indicator of spatial auto-correlation measured local correlation.

Findings: Percentages of live births to adolescent mothers for the whole country were 19.3% in 2010 and 17.5% in 2016. There is a heterogeneous spatial distribution pattern for these percentages, being the highest percentages in the North region (24.8% in 2016) and the lowest percentages in the Southeast region of the country (14.3% in 2016). The Bayesian model showed that meso-regions with lower human development index values have higher percentages of live births to adolescent mothers.

Conclusion: Our findings suggest that adolescent pregnancy is deeply associated with environmental characteristics.