title: Risk factors associated with preterm birth according to gestational age at birth.
abstract: OBJECTIVE
  To identify and quantify risk factors associated with preterm birth, stratified by gestational age at birth.
  
  
  METHODS
  Three case-control analyses were done. Controls were pregnancies of > or =37 weeks of gestational age at birth. Cases were defined as: <28, 28-32, 33- <37 weeks of gestational age at birth respectively in the three case-control analyses. Women were categorized according to whether they carried single or multiple infants.
  
  
  RESULTS
  Obstetrical conditions (placenta previa, placental abruption), and maternal hypertension were significantly associated with preterm delivery in all case-control analyses (adjusted OR between 1.34-19.56, p < 0.05). Leading risk factors for preterm delivery in singleton pregnancies were placental abruption and placenta previa (adjusted ORs 4.85 and 4.13, p < 0.05). For multiple pregnancies they were polyhydramnios and maternal hypertension (adjusted ORs 4.39 and 2.45, p < 0.05).
  
  
  CONCLUSIONS
  Obstetrical conditions during the pregnancy and maternal hypertension are important risk factors for preterm birth.
authors.affiliation: Faculty of Pharmacy, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Ofori
authors.forename: Magali
authors.initials: M
authors.lastname: Le Tiec
authors.forename: Anick
authors.initials: A
authors.lastname: Bérard
mesh_terms: D000037:Abruptio Placentae / Q000453:epidemiology; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D016208:Databases, Factual; D005260:Female; D005865:Gestational Age; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000453:epidemiology; D016017:Odds Ratio; D010923:Placenta Previa / Q000453:epidemiology; D006831:Polyhydramnios / Q000453:epidemiology; D011247:Pregnancy; D011272:Pregnancy, Multiple; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology*; D011792:Quebec / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors