Keywords► macrosomia ► prevalence ► trends ► epidemiology ► maternal health ► child health AbstractPurpose To describe the trends in the prevalence of macrosomia (birth weight ! 4,000 g) according to gestational age in Brazil in the periods of 2001-2010 and 2012-2014. Methods Ecological study with data from the Brazilian Live Birth Information System (SINASC, in the Portuguese acronym) regarding singleton live newborns born from 22 gestational weeks. The trends in Brazil as a whole and in each of its five regions were analyzed according to preterm (22-36 gestational weeks) and term (37-42 gestational weeks) strata. Annual Percent Changes (APCs) based on the Prais-Winsten method and their respective 95% confidence intervals (CIs) were used to verify statistically significant changes in 2001-2010. Results In Brazil, the prevalence of macrosomic births was of 5.3% (2001-2010) and 5.1% (2012-2014). The rates were systematically higher in the North and Northeast Regions both in the preterm and in term strata. In the preterm stratum, the North Region presented the highest variation in the prevalence of macrosomia (þ137.5%) when comparing 2001 (0.8%) to 2010 (1.9%). In the term stratum, downward trends were observed in Brazil as a whole and in every region. The trends for 2012-2014 were more heterogeneous, with the prevalence systematically higher than that observed for 2001-2010. The APC in the preterm stratum (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) showed a statistically significant trend change in the North (APC: 15.4%; 95%CI: 0.6-32.3) and South (APC: 13.5%; 95%CI: 4.8-22.9) regions. In the term stratum, the change occurred only in the North region (APC:-1.5%; 95%CI: -2.5--0.5).