Table 3 Baseline demographic and clinical characteristic of the enrolled newborns and of their parents: postnatal conditions
| Â | wGA groups | |||
|---|---|---|---|---|
|  | 33+0d-34+6d (No. 737) | 35+0d-37+6d (No. 767) | ≥38+0d (No. 706) | Total (No. 2210) |
Presence of siblings | Â | Â | Â | Â |
  None | 472 (64.0) | 444 (57.9) | 394 (55.8) | 1310 (59.3) |
  ≤ 10 year | 223 (30.3) | 289 (37.7) | 280 (39.7) | 792 (35.8) |
  > 10 year | 42 (5.7) | 34 (4.4) | 32 (4.5) | 108 (4.9) |
Residential crowding | 88 (11.9) | 86 (11.2) | 53 (7.5) | 227 (10.3) |
Lack of breastfeeding | 209 (28.4) | 193 (25.2) | 80 (11.3) | 482 (21.8) |
Pollution exposure | 77 (10.4) | 102 (13.3) | 87 (12.3) | 266 (12.0) |
Exposure to parental smoking | 310 (42.1) | 320 (41.7) | 272 (38.5) | 902 (40.8) |
Indoor humidity | 75 (10.2) | 75 (9.8) | 72 (10.2) | 222 (10) |
Exposure to epidemic season | 437 (59.3) | 474 (61.8) | 412 (58.4) | 1323 (59.9) |
Hospitalization for bronchiolitis | 54 (7.3) | 41 (5.3) | 25 (3.5) | 120 (5.4) |