Children delivered in the city of Pelotas, Brazil's hospitals in 1982, 1993 and 2004, as well as their mothers, were the target population for three birth cohort studies. Continuing with the regular 11-year intervals, the 2015 cohort was launched to provide detailed information on maternal and child health time trends. Eligible mothers - those living in the urban area of Pelotas municipality and in the Jardim América neighbourhood (which became part of the municipality of Capão do Leão in May 1982) - were interviewed soon after delivery. Children born between 1 January and 31 December 2015 were eligible for inclusion as long as their mothers lived in the urban area of Pelotas as defined in the first birth cohort (1982).