Neonatal outcome of study cohort overall and by ABT group
| Outcome | n | Study cohort (N=1762) n (%)* | ABT group | P value | |||
| No ABT (n=548) n (%)* | ABT start, day 1 or 2 (n=973) n (%)* | ABT start, days 3–6 (n=147) n (%)* | ABT start, day ≥7 (n=94) n (%)* | ||||
| BPD | 1762 | 199 (11.3) | 8 (1.4) | 165 (17.0) | 21 (14.3) | 5 (5.3) | <0.001Chi |
| IVH (n=1758) | 1758 | 171 (9.7) | 13 (2.4) | 139 (14.3) | 11 (7.5) | 9 (9.6) | <0.001Chi |
| Grade I | 84 (4.8) | 10 (1.8) | 62 (6.4) | 8 (5.4) | 4 (4.3) | <0.001Fis | |
| Grade II | 40 (2.3) | 2 (0.3) | 34 (3.5) | 3 (2.0) | 2 (2.1) | <0.001Fis | |
| Grade III | 47 (2.7) | 1 (0.2) | 43 (4.4) | 0 (0.0) | 3 (3.2) | <0.001Fis | |
| Grade IV | 45 (2.6) | 1 (0.2) | 40 (4.1) | 1 (0.7) | 3 (3.2) | <0.001Fis | |
| LOS | 1762 | 173 (9.8) | 0 (0.0) | 115 (11.8) | 27 (18.4) | 31 (33.0) | <0.001Fis |
| FIP surgery (n=1760) | 1760 | 47 (2.7) | 0 (0.0) | 36 (3.7) | 9 (6.1) | 2 (2.1) | <0.001Fis |
| NEC surgery (n=1760) | 1760 | 29 (1.6) | 0 (0.0) | 22 (2.3) | 4 (2.7) | 3 (3.2) | <0.001Fis |
| ROP ≥3 (n=1411) | 1411 | 39 (2.2) | 0 (0.0) | 35 (3.6) | 3 (2.0) | 1 (1.1) | <0.001Fis |
| PVL | 1762 | 22 (1.2) | 2 (0.4) | 19 (1.8) | 1 (0.7) | 1 (1.1) | .06Fis |
| PDA surgery | 1762 | 20 (1.1) | 0 (0.0) | 20 (2.1) | 0 (0.0) | 0 (0.0) | <0.001Fis |
| Death | 1762 | 61 (3.5) | 1 (0.2) | 51 (5.2) | 7 (4.8) | 2 (2.1) | <0.001Fis |
* Unless otherwise stated.
ABT, antibiotic therapy; BPD, bronchopulmonary dysplasia; Chi, χ2 test; FIP, focal intestinal perforation; Fis, Fisher test; IVH, intraventricular haemorrhage; KW, Kruskall Wallis test; LOS, late-onset sepsis; NEC, necrotising enterocolitis; PDA, patent ductus arteriosus; PVL, periventricular leucomalacia; ROP, retinopathy of prematurity.