Methods used in the 1982, 1993, and 2004 birth cohort studies from Pelotas, Rio Grande do Sul State, Brazil, and a description of the socioeconomic conditions of participants' families

Abstract

Three birth cohorts are currently being followed in Pelotas, Southern Brazil, in IntroductionThe first Pelotas birth cohort took place in 1982 in the city of Pelotas, Southern Brazil 1 , prompted by an interest in studying birth conditions, including gestation, delivery, and newborn care, and in documenting the development of mother-child health indicators. Although the cohort study was originally intended as a perinatal study, its original subjects are still being studied to the present day, totaling 24 years of follow-up.Given the importance of monitoring epidemiological profiles in relation to health outcomes and risk factors, a second birth cohort study was begun in Pelotas in 1993, 11 years after the first 2 . The success of these two studies, as measured by the amount and relevance of publications and the training of post-graduate researchers, encouraged us to undertake a third birth cohort in the same city in 2004 3 .Standard medical records of health indicators have their limitations, including under-registration, incomplete coverage, a lack of standardization, and the fact that disaggregated statistics, such as socioeconomic status and skin color, are not possible 4 . Birth cohort studies have the advantage of involving the collection of data at a time close to its occurrence, in addition to allowing for efficient data quality control, minimizing the problems mentioned above. However, the recently renewed interest in cohort studies is largely due to Barker's hypothesis of the fetal ori-ARTIGO ARTICLE Barros AJD et al.

Preterm births, low birth weight, and intrauterine growth restriction in three birth cohorts in Southern Brazil: 1982, 1993 and 2004

“…In 1982, 1993, and 2004, all hospital-born children in the city of Pelotas were followed within three cohort studies using similar methods 7 . Maternity wards were visited on a daily basis, and all women who gave birth were interviewed within a few hours of delivery.…”

“…In 1982In , 1993, three birth cohort studies were conducted in the city; these studies included all hospital deliveries that occurred during these three years. Considering that less than 1% of deliveries in the city occurred outside hospitals 7 , this study has a solid populational basis. The perinatal data from these cohorts allowed for an analysis of trends in birth weight, preterm delivery, and intra-uterine growth restriction.…”

Developmental status at age 12 months according to birth weight and family income: a comparison of two Brazilian birth cohorts

“…A detailed description of the methodology of these studies has been published elsewhere 11 . Mothers responded to a questionnaire including items on reproductive, demographic, socioeconomic, and environmental variables, as described previously 11 .…”

Hospitalizations during infancy in three population-based studies in Southern Brazil: trends and differentials

“…In 1982, 1993, and 2004, all births that took place in Pelotas were followed in cohort studies using a similar methodology 18 . The city's maternity wards were visited on a daily basis, and mothers were interviewed in the first hours after delivery.…”

“…Independent variables included in the present report were sex, birth weight, and family income. In the three cohorts, newborns were weighed by maternity ward nurses immediately following delivery, using pediatric scales periodically calibrated by the research team 18 . Birth weight was analyzed in two ways: divided into five categories (< 2,000g, 2,000-2,499g, 2,500-2,999g, 3,000-3,499g, and ≥ 3,500g), and as a binary variable (< 2,500g or ≥ 2,500g).…”