Comparison of trends in survival rates of extremely preterm infants in the UK (Trent health region, London) and Switzerland
| Reference | Switzerland | Trent, UK30 | London, UK31 | |||
| Time period | 2000–1 | 2003–4 | 1994–9 | 2000–5 | 1991–5 | 1996–2000 |
| Study population | pb | pb | hb | |||
| mc | mc | sc | ||||
| ib/ob | ib/ob | ib only | ||||
| Total population | ||||||
| Live births, n | 220 | 204 | 682 | 669 | 76 | 70 |
| Survivors, n | 67 | 82 | 174 | 236 | 29 | 48 |
| Survivors, % | 31% | 40% | 26% | 35% | 38% | 69% |
| 22 weeks | ||||||
| Live births, n | 7 | 10 | 81 | 69 | 2 | 8 |
| Survivors, n | 0 | 0 | 0 | 0 | 0 | 4 |
| Survivors, % | 0% | 0% | 0% | 0% | 0% | 50% |
| 23 weeks | ||||||
| Live births, n | 29 | 37 | 148 | 131 | 9 | 13 |
| Survivors, n | 1 | 4 | 15 | 12 | 4 | 6 |
| Survivors, % | 3% | 11% | 10% | 9% | 44% | 46% |
| 24 weeks | ||||||
| Live births, n | 69 | 58 | 198 | 227 | 22 | 22 |
| Survivors, n | 17 | 19 | 40 | 82 | 11 | 18 |
| Survivors, % | 25% | 33% | 20% | 36% | 50% | 82% |
| 25 weeks | ||||||
| Live births, n | 115 | 99 | 255 | 242 | 43 | 27 |
| Survivors, n | 48 | 59 | 119 | 142 | 14 | 20 |
| Survivors, % | 42% | 60% | 47% | 59% | 33% | 74% |
hb, hospital-based; ib, inborn; mc, multicentre; ob, outborn; pb, population-based; sc, single centre.