Multivariate analysis of risk factors for grade III–IV PVH/IVH
| Confounding variables | No of infants | Odds ratio (95% CI) |
| Tocolysis | ||
| No therapy | 2013 | 1.0 |
| Magnesium sulphate | 341 | 0.8 (0.5 to 1.2) |
| Ritodrine | 263 | 0.3 (0.2 to 0.6) |
| Indomethacin | 177 | 1.0 (0.6 to 1.6) |
| Antenatal steroid therapy | ||
| Full | 1161 | 1.0 |
| Partial | 489 | 1.6 (1.1 to 2.4) |
| None | 1133 | 2.1 (1.5 to 2.9) |
| Multiple birth | ||
| Yes | 1159 | 0.9 (0.7 to 1.2) |
| No | 1635 | 1.0 |
| PROM (>6 hours) | ||
| Yes | 932 | 0.9 (0.6 to 1.1) |
| No | 1856 | 1.0 |
| Amnionitis | ||
| Yes | 329 | 1.0 (0.7 to 1.5) |
| No | 2461 | 1.0 |
| Delivery | ||
| Vaginal | 1097 | 1.3 (1.0 to 1.7) |
| Caesarean section | 1697 | 1.0 |
| Gestational age (weeks) | ||
| 24 to 25 | 293 | 5.3 (3.0 to 9.8) |
| 26 to 27 | 614 | 3.0 (1.9 to 5.0) |
| 28 to 29 | 871 | 2.2 (1.4 to 3.4) |
| ⩾30 | 1016 | 1.0 |
| Birth weight (g) | ||
| <750 | 290 | 0.9 (0.5 to 1.5) |
| 750 to 999 | 703 | 1.0 (0.6 to 1.6) |
| 1000 to 1249 | 890 | 0.9 (0.6 to 1.3) |
| ⩾1250 | 971 | 1.0 |
| One minute Apgar score | ||
| 0 to 3 | 506 | 2.0 (1.3 to 3.0) |
| 4 to 7 | 1159 | 1.4 (1.0 to 2.0) |
| ⩾8 | 1070 | 1.0 |
| Five minute Apgar score | ||
| 0 to 3 | 59 | 1.5 (0.8 to 2.8) |
| 4 to 7 | 556 | 1.0 (0.7 to 1.3) |
| ⩾8 | 2071 | 1.0 |
| RDS | ||
| Yes | 1799 | 2.3 (1.5 to 3.6) |
| No | 995 | 1.0 |
| PDA | ||
| Yes | 797 | 1.3 (1.0 to 1.6) |
| No | 1996 | 1.0 |
| Mechanical ventilation | ||
| Yes | 1997 | 4.1 (2.1 to 9.2) |
| No | 797 | 1.0 |
| Pneumothorax | ||
| Yes | 235 | 1.8 (1.3 to 2.5) |
| No | 2559 | 1.0 |
| Sepsis | ||
| Yes | 979 | 0.8 (0.6 to 1.1) |
| No | 1815 | 1.0 |
PVH, Periventricular haemorrhage; IVH, intraventricular haemorrhage; PROM, premature rupture of the membranes; RDS, respiratory distress syndrome; PDA, patent ductus arteriosus.