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.