Late preterm birth in the far south of Brazil: a population based study

Objectives: to describe the prevalence of late preterm birth (LPB) and identify factors associated with its occurrence in the municipality of Rio Grande, RS. Methods: a standardized questionnaire was applied to allpuerperal women resident in the municipality who had children in theyear 2013. Preterm birth was defined as birth occur-ring between the 34th and 36th week of gestation, preferably evaluated by means of ultra-sonography in the 6th to 20th weeks. The analysis used Poisson regression with robust adjustment of variance, following the hierarchical model.The effect measure used was the preva-lence ratio (PR). Results: of the 2286 births included in the study, 11.8% (CI95%: 10.5-13.1) were LPBs. After adjusted analysis, the PRfor occurrence of LPB among black-skinned motherswas 1.40 (1.01-1.96) in relation to white-skinned women; 1.74 (1.23-2.45) among those who attended less than sixprenatal consults compared to those who attended nine or more; the PR was 1.36 (1.11-1.68) for those classified as depressives compared to others and 1.29 (1.01-1.65) for those undergoing caesarian. Conclusions: the results suggest the existence of inequality in relation to skin color and the important impact of the number ofprenatal consults on the outcome. More appropriately designed studies are needed to confirm the causal relation among maternal depression, caesarian and LPB.