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Table 4 Adjusted estimates of risk factors for influenza in pregnant admissions overall and by subtype/lineage

From: Epidemiology of influenza in pregnant women hospitalized with respiratory illness in Moscow, 2012/2013–2015/2016: a hospital-based active surveillance study

  Adjusted odds ratio (95% CI) a
  Any influenza A(H1N1)pdm09 A(H3N2) B/Yamagata B/Victoria
Characteristic N = 825 N = 361 N = 224 N = 106 N = 76
Age (in years) b 1.02 (1.00–1.04) 1.03 (1.01–1.06) 1.00 (0.97–1.03) 1.09 (1.04–1.13) 0.96 (0.91–1.00)
Trimester
 First (0–13 weeks) 1 1 1 1 1
 Second (14–26 weeks) 1.19 (0.92–1.53) 1.17 (0.82–1.66) 0.89 (0.58–1.35) 1.34 (0.75–2.51) 2.28 (1.10–4.74)
 Third (27–42 weeks) 1.12 (0.86–1.46) 0.82 (0.56–1.19) 1.23 (0.82–1.87) 1.57 (0.86–2.88) 1.58 (0.72–3.44)
Underlying conditions
 No 1 1 1 1 1
 Yes 1.56 (1.16–2.08) 1.78 (1.19–2.67) 1.91 (1.25–2.93) 1.24 (0.66–2.34) 2.01 (0.39–3.15)
  1. aAdjusted for age, trimester, comorbidity, hospital admission in the previous 12 months, time to swab, and season-week
  2. bComparison group was influenza-negative pregnant women