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Table 2 Characteristics of pregnant admissions by influenza infection status

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

Characteristic Influenza positive Influenza negative OR (95% CI) P-value
N = 825 N = 923
Age group, n (%)
 15–19 years 27 (3.3) 42 (4.6) 1  
 20–24 years 153 (18.6) 214 (23.2) 1.11 (0.66–1.88) 0.692
 25–29 years 327 (39.6) 341 (36.9) 1.49 (0.90–2.48) 0.122
 30–34 years 206 (25.0) 214 (23.2) 1.50 (0.89–2.52) 0.128
 35–39 years 89 (10.8) 94 (10.2) 1.47 (0.84–2.59) 0.178
 40–44 years 23 (2.8) 18 (2.0) 1.99 (0.91–4.35) 0.086
Median age in years (range) 28.5 (15–44) 28 (15–44) 1.02 (1.00–1.04) 0.021
Underlying conditions, n (%)
 One or more 136 (16.5) 106 (11.5) 1.52 (1.16–1.99) 0.003
 Cardiovascular disease 28 (3.4) 23 (2.5) 1.37 (0.78–2.40) 0.268
 Chronic obstructive pulmonary disease 12 (1.5) 8 (0.9) 1.68 (0.69–4.14) 0.256
 Asthma 10 (1.2) 6 (0.7) 1.87 (0.68–5.17) 0.227
 Diabetes a 0 (0.0) 3 (0.3) 0.29 (0.00–2.71) 0.294
 Renal impairment 68 (8.2) 54 (5.9) 1.44 (0.99–2.09) 0.053
 Cirrhosis 9 (1.1) 8 (0.9) 1.26 (0.48–3.28) 0.637
 Neuromuscular a 1 (0.1) 0 (0.0) 1.12 (0.03–∞) 0.944
 Neoplasm 2 (0.2) 2 (0.2) 1.12 (0.16–7.95) 0.912
 Rheumatic disease a 0 (0.0) 1 (0.1) 1.12 (0.00–43.63) 1.000
 Antiviral treatment before admission, n (%) 8 (1.0) 11 (1.2) 0.81 (0.32–2.02) 0.652
 Influenza vaccination, n (%) 3 (0.4) 3 (0.3) 0.99 (0.97–1.01) 0.392
Trimester of pregnancy, n (%)
 First (0–13 weeks) 177 (21.5) 221 (23.9) 1  
 Second (14–26 weeks) 355 (43.0) 372 (40.3) 1.19 (0.93–1.52) 0.162
 Third (27–42 weeks) 291 (35.3) 325 (35.2) 1.12 (0.87–1.44) 0.388
 Gestational age at admission (weeks), median (range) 23 (1–41) b 23 (3–42) c 1.00 (0.99–1.01) 0.872
Smoking habits, n (%)
 Never smoked 563 (68.2) 602 (65.2) 1  
 Past smoker 225 (27.3) 268 (29.0) 0.90 (0.73–1.11) 0.317
 Current smoker 37 (4.5) 53 (5.7) 0.75 (0.48–1.15) 0.188
Socioeconomic class, n (%)
 Managerial 359 (43.5) 383 (41.5) 1  
 Skilled 360 (43.6) 425 (46.0) 0.9 (0.74–1.10) 0.324
 Unskilled 34 (4.1) 52 (5.6) 0.7 (0.44–1.10) 0.121
 Other 72 (8.7) 63 (6.8) 1.22 (0.84–1.76) 0.29
Time from onset of symptoms to swabbing, n (%)
 0–2 days 559 (67.8) 541 (58.6) 1  
 3–4 days 228 (27.6) 280 (30.3) 0.79 (0.64–0.97) 0.027
 5–7 days 38 (4.6) 102 (11.1) 0.36 (0.24–0.53) 0.001
 Days from onset of symptoms to swabbing, median (range) 2 (0–7) 2 (0–7) 0.87 (0.82–0.93) 0.001
  1. aOdds ratio estimated by exact logistic regression
  2. bN = 823
  3. cN = 918