Proportions of extremely low birthweight (500–999 g) compared with very low birthweight (500–1499 g) infants in the study cohort and national populations in each country in 1993 and 1994
| Infants 500–999 g birthweight | Infants 500–1499 g birthweight | % infants 500–999 g birthweight | χ2 | p Value | |
| Scotland | |||||
| Study cohort (8 intensive care units) | 338 | 867 | 39 | ||
| All live births | 458 | 1216 | 38 | 0.37 | 0.54 |
| Australia | |||||
| Study cohort (6 intensive care units) | 515 | 1449 | 36 | ||
| All live births | 1820 | 4770 | 38 | 0.1 | 0.75 |