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Table 2 Associations for age at first hospital admission for acute gastroenteritis by mode of birth, timing of birth and infant formula only at birth for the overall study and selected sub-populations, NSW 2001–2011a

From: Gestational age, mode of birth and breastmilk feeding all influence acute early childhood gastroenteritis: a record-linkage cohort study

  Study Population Low-riskc Healthy controlsd From 1 July 2007e Primaryf 1-yearg 2-yearh
Study population (N) 893,360 435,417 610,538 387,539 893,360 893,360 893,360
Children admitted (%) 4.6 4.6 6.8 2.3 4.1 1.6 3.0
  aHR (95 % CI) aHR (95 % CI) aHR (95 % CI) aHR (95 % CI) aHR (95 % CI) aHR (95 % CI) aHR (95 % CI)
Mode of birth        
Vaginal birth – spontaneous onset of labour 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference]
Vaginal birth – labour induction 1.12 (1.09–1.15) 1.12 (1.08–1.16) 1.15 (1.12–1.18) 1.10 (1.04–1.16) 1.13 (1.10–1.16) 1.18 (1.13–1.23) 1.14 (1.10–1.17)
Caesarean section – pre-labour 1.19 (1.16–1.23) 1.17 (1.11–1.22) 1.24 (1.20–1.27) 1.20 (1.13–1.27) 1.20 (1.16–1.23) 1.24 (1.18–1.31) 1.22 (1.17–1.26)
Caesarean section – spontaneous onset of labour 1.20 (1.16–1.25) 1.15 (1.08–1.22) 1.24 (1.20–1.29) 1.22 (1.13–1.33) 1.21 (1.16–1.26) 1.25 (1.17–1.34) 1.24 (1.18–1.30)
Caesarean section – labour induction 1.23 (1.18–1.29) 1.31 (1.22–1.41) 1.28 (1.22–1.34) 1.18 (1.07–1.29) 1.23 (1.17–1.29) 1.33 (1.23–1.43) 1.26 (1.20–1.33)
Gestational age (weeks)        
33–36 1.23 (1.18–1.29) - 1.44 (1.37–1.50) 1.28 (1.16–1.40) 1.23 (1.17–1.29) 1.28 (1.19–1.38) 1.24 (1.17–1.31)
37–38 1.15 (1.12–1.17) 1.14 (1.10–1.19) 1.21 (1.18–1.24) 1.17 (1.11–1.23) 1.14 (1.11–1.17) 1.19 (1.15–1.24) 1.15 (1.12–1.19)
39–42 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference] 1.00 [Reference]
Formula-only feedingb 1.18 (1.11–1.24) 1.17 (1.08–1.26) 1.19 (1.14–1.25) 1.20 (1.14–1.28) 1.17 (1.11–1.24) 1.34 (1.25–1.44) 1.24 (1.17–1.31)
  1. CI Confidence Interval, aHR Hazard Ratio. aAll models were adjusted for maternal country of birth, maternal smoking during pregnancy, socio-economic advantage, parity, diabetes, hypertension, baby’s sex, year of birth, birthweight, and length of stay and infections in the birth admission (AGE or ICD-10-AM: P35-P39), with the following exceptions; for the low-risk group diabetes and hypertension were not applicable and admission to a special care nursery or neonatal intensive care was able be included as preterm was not in the sub-group, for births occurring after 1 July 2007, the indicator for pre/post introduction of universal rotavirus vaccination was not applicable
  2. bReference category is absence of risk factor and the reported aHR includes uses imputed values
  3. cPopulation restricted to low risk pregnancies: 10th–90th percentile birthweight for gestational age and sex, cephalic presenting, term births (≥37 weeks) to mothers aged 20–34 years without medical conditions
  4. dPopulation restricted to children with one or more AGE hospital admissions or no hospital admissions
  5. ePopulation restricted to children born after the inclusion of rotavirus vaccination in the Australian National Immunisation Program (1 July 2007)
  6. fAge at first hospital admission with a primary diagnosis of AGE was used to define the event
  7. gThe age at first AGE hospital admission within the first year of life was used to define the event. For censored individuals, age was recorded as the earliest of death, first birthday, or end of the study period (30 June 2012)
  8. hThe age at first AGE hospital admission within the first two years of life was used to define the event. For censored individuals, age was recorded as the earliest of death, second birthday, or end of the study period (30 June 2012)