Characteristics of the delivery and infant associated with the risk of hospital admission for bronchiolitis in infancy
| Number children with bronchiolitis (total number with each characteristic) | % with bronchiolitis | p Value | Adjustment for year of birth, social class, mother’s age, parity, smoking and sex: OR (95% CI) | |
|---|---|---|---|---|
| Number of babies | ||||
| 1 | 2009 (238 311) | 0.84 | <0.001 | 1 (1) |
| 2 | 76 (5348) | 1.42 | 1.86 (1.37 to 2.54) | |
| Total | 2085 (243 659) | 0.86 | ||
| Birth weight of baby (kg) | ||||
| 1–1.499 | 27 (1028) | 2.63 | <0.001 | 3.74 (2.32 to 6.01) |
| 1.5–1.999 | 57 (2745) | 2.08 | 2.34 (1.59 to 3.44) | |
| 2–2.499 | 174 (10 079) | 1.73 | 1.90 (1.50 to 2.41) | |
| 2.5–2.999 | 428 (43 857) | 0.98 | 1.14 (0.96 to 1.35) | |
| 3–3.499 | 777 (95 463) | 0.81 | 1 (1) | |
| 3.5–3.999 | 450 (68 984) | 0.65 | 0.76 (0.64 to 0.89) | |
| 4–5.499 | 163 (20 661) | 0.79 | 0.90 (0.71 to 1.14) | |
| Total | 2076 (242 817) | 0.85 | ||
| Lowest 10th percentile of birth weight for gestational age | ||||
| No | 1509 (195 332) | 0.77 | <0.001 | 1 (1) |
| Yes | 257 (21 694) | 1.18 | 1.34 (1.10 to 1.63) | |
| Total | 1766 (217 026) | 0.81 | ||
| Gestational age (weeks) | ||||
| 28–36 | 184 (11 997) | 1.53 | <0.001 | 2.24 (1.78 to 2.82) |
| 37 | 114 (10 275) | 1.11 | 1.62 (1.23 to 2.14) | |
| 38 | 254 (27 314) | 0.93 | 1.23 (0.99 to 1.52) | |
| 39 | 352 (45 299) | 0.78 | 0.97 (0.80 to 1.19) | |
| 40 | 429 (59 596) | 0.72 | 1 (1) | |
| 41 | 246 (42 113) | 0.58 | 0.82 (0.66 to 1.02) | |
| 42 | 105 (12 811) | 0.82 | 1.04 (0.76 to 1.40) | |
| 43 | 32 (3603) | 0.89 | 1.21 (0.76 to 1.95) | |
| 44+ | 57 (4742) | 1.20 | 1.02 (0.67 to 1.55) | |
| Total | 1773 (217 750) | 0.81 | ||
| Infant feeding | ||||
| Breast | 796 (113 432) | 0.70 | <0.001 | 1 (1) |
| Artificial | 758 (49 245) | 1.54 | 1.35 (1.18 to 1.55) | |
| Total | 1554 (162 677) | 0.96 | ||
| Caesarean delivery | ||||
| No | 1895 (224 350) | 0.84 | 0.026 | 1 (1) |
| Yes | 183 (18 248) | 1.00 | 1.35 (1.03 to 1.53) | |
| Total | 2078 (242 598) | 0.86 | ||
| Presentation | ||||
| Vertex | 1510 (153 258) | 0.99 | 0.28 | 1 (1) |
| Other | 12 (1528) | 0.79 | 1.37 (1.03 to 1.81) | |
| Breech | 76 (6578) | 1.16 | 0.76 (0.36 to 1.60) | |
| Total | 1598 (161 364) | 0.99 | ||
| Apgar score at 1 min | ||||
| 1–7 | 437 (45 935) | 0.95 | 0.015 | 1.29 (1.01 to 1.66) |
| 8–9 | 1288 (146 938) | 0.88 | 1.07 (0.86 to 1.34) | |
| 10 | 209 (28 015) | 0.75 | 1 (1) | |
| Total | 1934 (220 888) | 0.88 | ||
| Apgar score at 5 min | ||||
| 1–7 | 34 (2758) | 1.23 | 0.16 | 1.07 (0.67 to 1.72) |
| 8–9 | 130 (11 133) | 1.17 | 1.30 (1.05 to 1.62) | |
| 10 | 1360 (134 510) | 1.01 | 1 (1) | |
| Total | 1524 (148 401) | 1.03 | ||
| Sex | ||||
| Male | 1216 (125 358) | 0.97 | <0.001 | 1 (1) |
| Female | 871 (118 344) | 0.74 | 0.74 (0.66 to 0.84) | |
| Total | 2087 (243 702) | 0.86 | ||
Data from the Oxford Record Linkage Study specialist maternity dataset.