To analyse trends of social inequality in breastfeeding and infant formula (IF) use in Latin America between 1990 and 2010 decades.

Time-series cross-sectional study with data from Demographic and Health Surveys. We described the prevalence of exclusive breastfeeding (EBF), breastfeeding between 6 and 12 months (BF6-12) and IF for infants under 6 months (IF < 6) and between 6 and 12 months (IF6-12). Social inequalities were assessed using the slope index of inequality (SII) and concentration index (CIX). Trends in the prevalence of breastfeeding, IF and index of social inequality were analysed by a linear regression model with weighted least squares variance.

Bolivia, Colombia, Dominican Republic, Guatemala, Haiti and Peru.

51·358 alive infants younger than 12 months.

Five countries showed an increasing trend for EBF and BF6-12, four increased for IF < 6 and six for IF6-12. Simultaneous decrease in IF < 6 (Colombia: −0·3/year; Haiti: −0·02/year) and increase in EBF (Colombia: +2·0/year; Haiti: +1·9/year) were observed only in two countries. EBF prevalence was high in the lowest income quintiles in five countries, and IF prevalence was high in the highest income quintiles in all countries and over the decades. For BF6-12, a decrease in inequality (prevalence increased in the highest quintile) was observed in Guatemala (SII1995 = −0·42; SII2015 = −0·28) and the Dominican Republic (SII1996 = −0·54; SII2013 = −0·26). Guatemala was the only country showing a decrease in inequality for BF (SII = −0·005; CIX = −0·0035) and an increase for IF (SII = 0·022; CIX = 0·01).

The inequality in BF and IF remained over time. However, inequality in IF < 6 has decreased because low-income infants have increased use and high-income infants have decreased.