title: Prevalence and risk factors related to preterm birth in Brazil.
abstract: BACKGROUND
  The rate of preterm birth has been increasing worldwide, including in Brazil. This constitutes a significant public health challenge because of the higher levels of morbidity and mortality and long-term health effects associated with preterm birth. This study describes and quantifies factors affecting spontaneous and provider-initiated preterm birth in Brazil.
  
  
  METHODS
  Data are from the 2011-2012 "Birth in Brazil" study, which used a national population-based sample of 23,940 women. We analyzed the variables following a three-level hierarchical methodology. For each level, we performed non-conditional multiple logistic regression for both spontaneous and provider-initiated preterm birth.
  
  
  RESULTS
  The rate of preterm birth was 11.5 %﻿, (95 % confidence 10.3 % to 12.9 %) 60.7 % spontaneous - with spontaneous onset of labor or premature preterm rupture of membranes - and 39.3 % provider-initiated, with more than 90 % of the last group being pre-labor cesarean deliveries. Socio-demographic factors associated with spontaneous preterm birth were adolescent pregnancy, low total years of schooling, and inadequate prenatal care. Other risk factors were previous preterm birth (OR 3.74; 95 % CI 2.92-4.79), multiple pregnancy (OR 16.42; 95 % CI 10.56-25.53), abruptio placentae (OR 2.38; 95 % CI 1.27-4.47) and infections (OR 4.89; 95 % CI 1.72-13.88). In contrast, provider-initiated preterm birth was associated with private childbirth healthcare (OR 1.47; 95 % CI 1.09-1.97), advanced-age pregnancy (OR 1.27; 95 % CI 1.01-1.59), two or more prior cesarean deliveries (OR 1.64; 95 % CI 1.19-2.26), multiple pregnancy (OR 20.29; 95 % CI 12.58-32.72) and any maternal or fetal pathology (OR 6.84; 95 % CI 5.56-8.42).
  
  
  CONCLUSIONS
  The high proportion of provider-initiated preterm birth and its association with prior cesarean deliveries and all of the studied maternal/fetal pathologies suggest that a reduction of this type of prematurity may be possible. The association of spontaneous preterm birth with socially-disadvantaged groups reaffirms that the reduction of social and health inequalities should continue to be a national priority.
authors: National School of Public Health - Oswaldo Cruz Foundation, Rua Leopoldo Bulhões, 1480, sala 809, Manguinhos, Rio de Janeiro, CEP 21041-210, Brazil. ducaleal@gmail.com.
authors: Maria do Carmo
authors: MD
authors: Leal
authors: National School of Public Health - Oswaldo Cruz Foundation, Rua Leopoldo Bulhões, 1480, sala 809, Manguinhos, Rio de Janeiro, CEP 21041-210, Brazil.
authors: Ana Paula
authors: AP
authors: Esteves-Pereira
authors: National Institute of Women, Children and Adolescents Health Fernandes Figueira, Oswaldo Cruz Foundation, Avenida Rui Barbosa 716 - Flamengo, Rio de Janeiro, RJ, Brazil.
authors: Marcos
authors: M
authors: Nakamura-Pereira
authors: National Health Agency - Ministry of Health, Av. Augusto Severo, 84 - Glória, Rio de Janeiro, RJ, 20021-040, Brazil.
authors: Jacqueline Alves
authors: JA
authors: Torres
authors: National School of Public Health - Oswaldo Cruz Foundation, Rua Leopoldo Bulhões, 1480, sala 809, Manguinhos, Rio de Janeiro, CEP 21041-210, Brazil.
authors: Mariza
authors: M
authors: Theme-Filha
authors: National Institute of Infectious Disease, Oswaldo Cruz Foundation, Avenida Brasil 4.365 - Manguinhos, Rio de Janeiro, RJ, CEP 21040-900, Brazil.
authors: Rosa Maria Soares Madeira
authors: RM
authors: Domingues
authors: National Institute of Women, Children and Adolescents Health Fernandes Figueira, Oswaldo Cruz Foundation, Avenida Rui Barbosa 716 - Flamengo, Rio de Janeiro, RJ, Brazil.
authors: Marcos Augusto Bastos
authors: MA
authors: Dias
authors: National Institute of Women, Children and Adolescents Health Fernandes Figueira, Oswaldo Cruz Foundation, Avenida Rui Barbosa 716 - Flamengo, Rio de Janeiro, RJ, Brazil.
authors: Maria Elizabeth
authors: ME
authors: Moreira
authors: National School of Public Health - Oswaldo Cruz Foundation, Rua Leopoldo Bulhões, 1480, sala 809, Manguinhos, Rio de Janeiro, CEP 21041-210, Brazil.
authors: Silvana Granado
authors: SG
authors: Gama
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002648:Child; D005260:Female; D006282:Health Personnel; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications / Q000517:prevention & control*; D047928:Premature Birth / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D055815:Young Adult
keywords: Brazil; Provider-initiated preterm birth; Risk factors; Spontaneous preterm birth; pPROM