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Table 2 Association between maternal and offspring preterm birth, Manitoba, Canada, 1980–2016

From: Revisiting the association between maternal and offspring preterm birth using a sibling design

Maternal gestational age Infant’s preterm birth cases/No of births Preterm birth rate, % URR 95% CI ARR c 95% CI
Population cohorta (N = 79,198)
 Not Preterm 4588/75,427 6.08 1.00 Reference 1.00 Reference
 Preterm (24–36 weeks) 325/3771 8.62 1.42 1.27, 1.58 1.39 1.25, 1.54
 Very Preterm (24–31 weeks) 35/326 10.74 1.77 1.28, 2.42 1.76 1.29, 2.41
 Moderately Preterm (32–36 weeks) 290/3445 8.43 1.38 1.24, 1.55 1.35 1.21, 1.51
Sibling subcohortb (N = 2499)
 Not Preterm 143/1430 10.00 1.00 Reference 1.00 Reference
 Preterm (24–36 weeks) 109/1069 10.20 1.02 0.77, 1.36 1.02 0.77, 1.34
 Very Preterm (24–31 weeks) 7/80 8.75 0.88 0.39, 1.96 0.88 0.38, 2.02
 Moderately Preterm (32–36 weeks) 102/989 10.31 1.03 0.77, 1.38 1.03 0.78, 1.36
  1. Abbreviations: URR Unadjusted Relative Risk, ARR Adjusted Relative Risk, CI confidence intervals
  2. aAnalyzed with a log-binomial regression model
  3. bAnalyzed with a GEE fixed-effects log-binomial regression model
  4. cAdjusted for whether mother moved or had a substance abuse diagnosis in year before birth of child, child’s birth year, mother’s age at birth of child, neighborhood location and SES at birth of child, child’s sex and child’s birth order