The 1993 Pelotas Birth Cohort is one of four large population-based cohorts based within the Brazilian city of Pelotas. The first cohort is from 1982, and the development of a new cohort began every 11 years (1993, 2004, and 2015). All children born between January 1st and December 31st, 1993, living in the urban area of ​​Pelotas, are part of the current study. During the whole of 1993, all maternity hospitals in the city were visited daily, and 5,265 births from women living in the city were recorded. Of these, 5,249 agreed to take part in the longitudinal study; 50.3% were female, 18.4% belonged to very poor families (less than US$ 100 per month), 9.8% presented low birth weight, 10.8% were born pre-term, and 30.5% were delivered through caesarean sections.