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Table 1 Description of infants born during 19962004 by gestational age categories

From: Persistent recurring wheezing in the fifth year of life after laboratory-confirmed, medically attended respiratory syncytial virus infection in infancy

  Gestational age, wk  
  32–33 34–36 37 38–40 ≥ 41 All gestational ages
N 936 4,665 4582 51,049 11,370 72,602
Male sex, % 51.07 54.81 53.40 50.44 50.71 50.96
Race, %*       
 White 46.79 43.09 39.90 42.87 47.65 43.50
 African-American 11.32 10.40 9.41 8.57 9.30 8.89
 Asian 16.35 19.85 23.42 20.74 15.27 19.94
 Hispanic 16.99 18.93 20.32 21.25 20.81 20.92
 Other/unknown 8.55 7.74 6.96 6.56 6.97 6.75
Maternal age, y, %       
 <18 2.24 1.29 1.18 1.19 1.49 1.25
 18–34 67.20 68.75 70.76 73.58 74.64 73.17
 >35 30.56 29.97 28.07 25.23 23.87 25.57
Family history of asthma, %       
 None 93.91 94.23 94.43 94.82 95.15 94.80
 Father only 2.03 1.63 1.66 1.49 1.37 1.50
 Mother only 4.06 4.14 3.84 3.60 3.42 3.63
 Both parents 0.00 0.00 0.07 0.09 0.06 0.08
31 sibling <5 y of age in home, % 42.95 42.17 39.57 39.51 32.22 38.58
Congenital anomaly present, % 13.14 10.33 7.77 6.52 6.24 6.88
Small for gestational age, %§ 4.59 3.41 2.23 1.25 0.67 1.40
Oxygen exposure|| and BPD, %       
 No oxygen, no BPD 55.77 86.13 96.49 97.77 96.31 96.17
 <200 hours oxygen, no BPD 37.50 12.24 3.12 1.95 3.26 3.35
3200 hours oxygen, no BPD 5.24 1.29 0.37 0.25 0.40 0.41
 BPD 1.50 0.34 0.02 0.03 0.04 0.07
Unspecified respiratory hospitalization %# 15.92 15.05 12.40 8.09 7.19 8.77
Laboratory-confirmed, medically attended RSV infection, %** 3.95 2.98 2.14 1.64 1.36 1.74
 Admitted to hospital, %‡‡ 2.46 1.31 0.87 0.63 0.49 0.69
 Treated as outpatient, %§§ 1.50 1.67 1.27 1.00 0.87 1.05
Laboratory-confirmed, medically attended infection with other pathogen, %†† 0.64 0.58 0.31 0.28 0.25 0.30
 Admitted to hospital, %‡‡ 0.53 0.28 0.13 0.13 0.11 0.14
 Treated as outpatient, %§§ 0.11 0.3 0.17 0.16 0.14 0.16
  1. Abbreviations: BPD Bronchopulmonary dysplasia, CI Confidence interval, RSV Respiratory syncytial virus, wk week, y year.
  2. *Classification of race/ethnicity in this study was based on the race of infants' mothers, as self-reported to the birth certificate clerk interviewing them at the Kaiser Permanente hospitals described in this study. Race was assessed in this study because of the well-known differences in RSV infection severity by race.
  3. Ascertained by electronic scanning of parental records, which included encounters and diagnoses identified in the Significant Problem List by the parent’s physician.
  4. See text for list of included International Classification of Diseases codes.
  5. §Based on the algorithm of Brenner WE, et al. Am J Obstet Gynecol. 1976;126:555–564.
  6. ||Oxygen exposure, in hours, during the birth hospitalization. See text for details.
  7. All infants with BPD had ≥200 hours of oxygen exposure during the neonatal period.
  8. #Hospitalization for pneumonia or other respiratory illness without laboratory confirmation for RSV or the other pathogens listed in footnote ††.
  9. **Medically attended visit where positive RSV direct fluorescent antibody test or viral culture occurred within ± 14 days of visit.
  10. ††Medically attended encounter where a positive test result (direct fluorescent antibody test, viral culture, or bacterial culture) for adenovirus, influenza virus, parainfluenza virus 1 or 2, or Bordetella pertussis occurred within ± 14 days of encounter.
  11. ‡‡ The encounter included a hospital admission.
  12. §§ The encounter included outpatient care only.