title: The worldwide incidence of preterm birth: a systematic review of maternal mortality and morbidity.
abstract: OBJECTIVE
  To analyse preterm birth rates worldwide to assess the incidence of this public health problem, map the regional distribution of preterm births and gain insight into existing assessment strategies.
  
  
  METHODS
  Data on preterm birth rates worldwide were extracted during a previous systematic review of published and unpublished data on maternal mortality and morbidity reported between 1997 and 2002. Those data were supplemented through a complementary search covering the period 2003-2007. Region-specific multiple regression models were used to estimate the preterm birth rates for countries with no data.
  
  
  RESULTS
  We estimated that in 2005, 12.9 million births, or 9.6% of all births worldwide, were preterm. Approximately 11 million (85%) of these preterm births were concentrated in Africa and Asia, while about 0.5 million occurred in each of Europe and North America (excluding Mexico) and 0.9 million in Latin America and the Caribbean. The highest rates of preterm birth were in Africa and North America (11.9% and 10.6% of all births, respectively), and the lowest were in Europe (6.2%).
  
  
  CONCLUSIONS
  Preterm birth is an important perinatal health problem across the globe. Developing countries, especially those in Africa and southern Asia, incur the highest burden in terms of absolute numbers, although a high rate is also observed in North America. A better understanding of the causes of preterm birth and improved estimates of the incidence of preterm birth at the country level are needed to improve access to effective obstetric and neonatal care.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, USA.
authors.forename: Stacy
authors.initials: S
authors.lastname: Beck
authors.forename: Daniel
authors.initials: D
authors.lastname: Wojdyla
authors.forename: Lale
authors.initials: L
authors.lastname: Say
authors.forename: Ana Pilar
authors.initials: AP
authors.lastname: Betran
authors.forename: Mario
authors.initials: M
authors.lastname: Merialdi
authors.forename: Jennifer Harris
authors.initials: JH
authors.lastname: Requejo
authors.forename: Craig
authors.initials: C
authors.lastname: Rubens
authors.forename: Ramkumar
authors.initials: R
authors.lastname: Menon
authors.forename: Paul F A
authors.initials: PF
authors.lastname: Van Look
mesh_terms: D019049:Developed Countries / Q000706:statistics & numerical data; D003906:Developing Countries / Q000706:statistics & numerical data; D014943:Global Health; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008428:Maternal Mortality; D047928:Premature Birth / Q000453:epidemiology*; D016387:Women's Health