title: The influence of refugee status and secondary migration on preterm birth.
abstract: It is unknown whether the risk of preterm birth (PTB) is elevated for forced (refugee) international migrants and whether prolonged displacement amplifies risk. While voluntary migrants who arrive from a country other than their country of birth (ie, secondary migrants) have favourable birth outcomes compared with those who migrated directly from their country of birth (ie, primary migrants), secondary migration may be detrimental for refugees who experience distinct challenges in transition countries. Our objectives were (1) to determine whether refugee status was associated with PTB and (2) whether the relation between refugee status and PTB differed between secondary and primary migrants.
  
  
  
  We conducted a retrospective population-based cohort study. Ontario immigration (2002-2010) and hospitalisation data (2002-2010) were linked to estimate adjusted cumulative odds ratios (ACOR) of PTB (22-31, 32-36, 37-41 weeks of gestation), with 95% CIs (95% CI) comparing refugees with non-refugees. We further included a product term between refugee status and secondary migration.
  
  
  
  Overall, refugees (N=12 913) had 17% greater cumulative odds of short gestation (ACOR=1.17, 95% CI 1.07 to 1.28) compared with non-refugees (N=110 640). Secondary migration modified the association between refugee status and PTB (p=0.007). Secondary refugees had 58% greater cumulative odds of short gestation (ACOR=1.58, 95% CI 1.25 to 2.00) than secondary non-refugees, while primary refugees had 12% greater cumulative odds of short gestation (ACOR=1.12, 95% CI 1.02 to 1.23) than primary non-refugee immigrants.
  
  
  
  Refugee status, jointly with secondary migration, influences PTB among migrants.
authors.affiliation: Centre for Research on Inner City Health, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Susitha
authors.initials: S
authors.lastname: Wanigaratne
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Donald C
authors.initials: DC
authors.lastname: Cole
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kate
authors.initials: K
authors.lastname: Bassil
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ilene
authors.initials: I
authors.lastname: Hyman
authors.affiliation: Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.affiliation: Centre for Research on Inner City Health, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Marcelo L
authors.initials: ML
authors.lastname: Urquia
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D005260:Female; D054624:Health Status Disparities; D006801:Humans; D009864:Ontario; D011157:Population Dynamics; D011159:Population Surveillance; D011247:Pregnancy; D047928:Premature Birth; D012036:Refugees; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D014171:Transients and Migrants / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: MIGRATION; PERINATAL EPIDEMIOLOGY; PREGNANCY; SOCIAL EPIDEMIOLOGY