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Table 3 Association between maternal and offspring preterm birth type in the population cohort a, Manitoba, Canada, 1980–2016

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

   Infant’s PTB cases/No of births PTB rate, % (N = 78,922) (N = 78,922) (N = 74,196) (N = 39,478)
Offspring outcome Maternal PTB type URR 95% CI ARRb 95% CI ARRc 95% CI ARRd 95% CI
Any PTB Not Preterm 4565/75,172 6.07 1.00 Reference 1.00 Reference 1.00 Reference 1.00 Reference
Spontaneous 195/2165 9.01 1.48 1.29, 1.70 1.47 1.28, 1.68 1.43 1.24, 1.65 1.28 1.03, 1.58
Provider-initiated 128/1585 8.08 1.33 1.12, 1.57 1.29 1.09, 1.52 1.23 1.02, 1.47 1.14 0.87, 1.48
Spontaneous PTB Not Preterm 3164/75,172 4.21 1.00 Reference 1.00 Reference 1.00 Reference 1.00 Reference
Spontaneous 149/2165 6.88 1.64 1.40, 1.92 1.61 1.38, 1.89 1.57 1.32, 1.85 1.33 1.04, 1.71
Provider-initiated 93/1585 5.87 1.39 1.14, 1.70 1.36 1.11, 1.66 1.32 1.07, 1.64 1.09 0.78, 1.52
Provider-initiated PTB Not Preterm 1401/75,172 1.86 1.00 Reference 1.00 Reference 1.00 Reference 1.00 Reference
Spontaneous 46/2165 2.12 1.14 0.85, 1.52 1.13 0.85, 1.52 1.11 0.82, 1.51 1.16 0.76, 1.77
Provider-initiated 35/1585 2.21 1.18 0.85, 1.65 1.13 0.81, 1.57 1.00 0.69–1.46 1.24 0.77, 1.99
  1. Abbreviations: PTB preterm birth, URR Unadjusted Relative Risk, ARR Adjusted Relative Risk, CI confidence intervals
  2. aAnalyzed with a log-binomial regression model. 276 children excluded due to missing information on maternal PTB type
  3. bAdjusted 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
  4. cRestricted to births 2000–2016 with complete information on additional covariates. Adjusted 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, child’s birth order, mother’s smoking status during pregnancy, mother’s education, inadequate prenatal care, receipt of employment income assistance in the year before the birth of the child, and whether mother had a partner
  5. dRestricted to one randomly child per mother (1995–2016). Adjusted 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