Profile of three Brazilian birth cohort studies in Ribeirao Preto, SP and Sao Luis, MA

We describe three birth cohort studies, respectively carried out in 1978/79 and 1994 in Ribeirao Preto, a city located in the most developed region of Brazil, and in 1997/98 in Sao Luis, a city located in a less developed region. The objective of the present report was to describe the methods used in these three studies, presenting their history, methodological design, objectives, developments, and difficulties faced along 28 years of research. The first Ribeirao Preto study, initially perinatal, later encompassed questions regarding the repercussions of intrauterine development on future growth and chronic adult diseases. The subjects were evaluated at birth (N = 6827), at school age ( N = 2861), at the time of recruitment for military service ( N = 2048), and at 23/25 years of age ( N = 2063). The study of the second cohort, which started in 1994 ( N = 2846), permitted comparison of aspects of perinatal health between the two groups in the same region, such as birth weight, mortality and health care use. In 1997/98, a new birth cohort study was started in Sao luis ( N = 2443), capital of the State of Maranhao. The 1994 Ribeirao Preto cohort and the Sao luis cohort are in the second phase of joint follow-up. These studies permit comparative temporal analyses in the same place (Ribeirao Preto 1978/79 and 1994) and comparisons of two contrasting populations regarding cultural, economic and sociodemographic conditions (Ribeirao Preto and Sao Luis).