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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