RPS Brazilian Birth Cohorts Consortium (Ribeirão Preto, Pelotas and São Luís): history, objectives and methods

This paper describes the history, objectives and methods used by the nine Brazilian cohorts of the RPS Brazilian Birth Cohorts Consortium (Ribeirão Preto, Pelotas and São Luís) Common thematic axes are identified and the objectives, baseline periods, follow-up stages and representativity of the population studied are presented. The Consortium includes three birth cohorts from Ribeirão Preto, São Paulo State (1978/1979, 1994 and 2010), four from Pelotas, Rio Grande do Sul State (1982, 1993, 2004 and 2015), and two from São Luís, Maranhão State (1997 and 2010). The cohorts cover three regions of Brazil, from three distinct states, with marked socioeconomic, cultural and infrastructure differences. The cohorts were started at birth, except for the most recent one in each municipality, where mothers were recruited during pregnancy. The instruments for data collection have been refined in order to approach different exposures during the early phases of life and their long-term influence on the health-disease process. The investigators of the nine cohorts carried out perinatal studies and later studied human capital, mental health, nutrition and precursor signs of noncommunicable diseases. A total of 17,636 liveborns were recruited in Ribeirão Preto, 19,669 in Pelotas, and 7,659 in São Luís. In the studies starting during pregnancy, 1,400 pregnant women were interviewed in Ribeirão Preto, 3,199 in Pelotas, and 1,447 in São Luís. Different strategies were employed to reduce losses to follow-up. This research network allows the analysis of the incidence of diseases and the establishment of possible causal relations that might explain the health outcomes of these populations in order to contribute to the development of governmental actions and health policies more consistent with reality.

Prevalence, mortality and risk factors associated with very low birth weight preterm infants: an analysis of 33 years

OBJECTIVE

To assess the prevalence, mortality and risk factors associated with the birth of very low birth weight preterm infants over a period of 33 years.

METHODS

Four cross-sectional studies were analyzed, using data from perinatal interviews of birth cohorts in the city of Pelotas collected in 1982, 1993, 2004, and 2015. Based on perinatal questionnaires, anthropometric measurements of newborns and death certificates were analyzed to obtain the prevalence rate, neonatal mortality, and risk factors (maternal age, income and type of delivery) for very low birth weight.

RESULTS

A total of 19,625 newborns were included in the study. In the years 1982, 1993, 2004, and 2015, there were, respectively, 5909, 5232, 4226, and 4258 births. The prevalence of very low birth weight was, respectively, 1.1% (n=64), 0.9% (n=46), 1.4% (n=61), and 1.3% (n=54). There was no statistical evidence of an increasing trend over time (p=0.11). Among the risk factors, family income in the three poorest quintiles was associated with prevalence rates that were approximately twice as high as in the richest quintile (p=0.003). Mortality per 1000 live births for neonates weighing <1500g decreased from 688 to 259 per thousand from 1982 to 2015 (p<0.001), but still represented 61% of neonatal deaths in the latter year.

CONCLUSION

Although mortality in very low birth weight decreased by more than 60% in recent years, this group still contributes with more than half of neonatal deaths. Low family income remains an important risk factor in this scenario.

Assisted reproductive technology: prevalence and associated factors in Southern Brazil

OBJECTIVE:

To assess the prevalence of successful assisted reproductive technology and to identify the associated factors.

METHODS:

This population-based birth cohort study was carried out with 4,333 pregnant women expected to deliver in 2015 in the urban area of Pelotas, Southern Brazil. Use of an assisted reproductive technology procedure, type of assisted reproductive technology [in vitro fertilization or intracytoplasmic sperm injection or artificial insemination], number of embryos transferred, success of embryo transfer, number of attempts, and reported reasons for seeking assisted reproductive technology were the main outcomes measured. Use of an assisted reproductive technology procedure was analyzed according to sociodemographic, nutritional, reproductive history, and behavioral characteristics. Unadjusted and adjusted analyses were performed by logistic regression.

RESULTS:

Among the 4,275 newborns enrolled in the Pelotas 2015 Birth Cohort Study, 18 births (0.4%) were conceived by assisted reproductive technology. Most cases of assisted reproductive technology were by in vitro fertilization (70.6%). All cycles were performed in private clinics under direct out-of-pocket payment. Even after controlling for confounders, maternal age > 35 years, nulliparity and high family monthly income were strongly associated with assisted reproductive technology.

CONCLUSIONS:

The use of assisted reproductive technology services was reported by only a few women in the Pelotas 2015 Birth Cohort Study. Our study highlights sociodemographic factors associated to assisted reproductive technology procedures. To better understand the patterns and barriers in overall use of assisted reproductive technology services over time, national-level trend studies in assisted reproductive technology treatments and outcomes, as well as studies exploring the characteristics of women who have sought this kind of treatment are needed in low-middle income countries.