title: Ethnic differences in preterm birth and its subtypes: the effect of a cumulative risk profile.
abstract: OBJECTIVE
  To explore the effect of potentially explanatory risk factors on ethnic differences in the prevalence of preterm birth (PTB) and its subtypes.
  
  
  METHODS
  Prospective population-based cohort study.
  
  
  METHODS
  Pregnant women from Amsterdam attending their first antenatal visit for obstetric care. A total of 8266 women participated (response rate 67%). Ethnicity was based on the country of birth of the pregnant woman's mother: the Netherlands, Surinam, the Antilles, Turkey, Morocco, Ghana and other non-Dutch countries. Exclusion criteria were multiple births and gestational age at delivery less than 24 weeks.
  
  
  METHODS
  Risk factors were obtained using a multilingual questionnaire and from the Dutch Perinatal Registration. Risk factors were summed into a cumulative risk score. Multiple logistic regression analyses were performed.
  
  
  METHODS
  Odds ratios with 95% CIs were calculated for total, spontaneous and iatrogenic (medically indicated) preterm births for the ethnic minority groups versus the Dutch reference group.
  
  
  RESULTS
  After adjustment for all risk factors, the Surinamese (OR 1.6, 95% CI 1.2-2.4), Ghanaian (OR 2.0, 95% CI 1.1-3.6) and Antillean (OR 1.6, 95% CI 0.8-3.3) women had a higher risk of PTB compared with the Dutch women, in particular for iatrogenic preterm birth (OR 2.1, 95% CI 1.0-4.4; OR 3.2, 95% CI 1.0-10.4; OR 3.6, 95% CI 1.1-11.2, respectively). The ethnic minority groups had a higher cumulative risk score (ranging from 2.1 to 3.7) compared with the Dutch group (1.8). Adjustment for the cumulative risk score considerably decreased the risk of PTB among the Surinamese (OR 1.2, 95% CI 0.9-1.7), Ghanaian (OR 1.3, 95% CI 0.8-2.3) and Antillean (OR 1.2, 95% CI 0.6-2.4) women.
  
  
  CONCLUSIONS
  A cumulation of risk factors, mainly observed among the ethnic minority groups, contributes to the explanation of ethnic differences in PTB prevalence.
authors.affiliation: Municipal Health Service, Department of Epidemiology, Documentation and Health Promotion, Amsterdam, The Netherlands. ggoedhart@ggd.amsterdam.nl
authors.forename: G
authors.initials: G
authors.lastname: Goedhart
authors.forename: M
authors.initials: M
authors.lastname: van Eijsden
authors.forename: M F
authors.initials: MF
authors.lastname: van der Wal
authors.forename: G J
authors.initials: GJ
authors.lastname: Bonsel
mesh_terms: D000328:Adult; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008423:Maternal Age; D008913:Minority Groups / Q000706:statistics & numerical data*; D009426:Netherlands / Q000453:epidemiology; D010342:Patient Acceptance of Health Care / Q000208:ethnology; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000208:ethnology* / Q000209:etiology; D011295:Prenatal Care / Q000706:statistics & numerical data