Neonatal data from infants with visual impairment caused by retinopathy of prematurity (ROP) in four consecutive survey periods in the Netherlands
| Period | 1975–1987 (survey 3) | 1986–1994 (survey 4) | 1994–2000 (survey 5) | 2000–2009 (survey 6) |
| Infants (n) | 76 | 87 | 51 | 42 |
| Male (%) | 47 | 58 | 59 | 74 |
| Mean gestational age (weeks)* | 28.7±2.7 | 27.5±2.5 | 27.7±2.4 | 27.4±2.0 |
| Mean birthweight (g)† | 1128±331 | 1071±385 | 942±306 | 912±385 |
| Multiple birth (%) | 18.9 | 20.7 | 31.4 | 31.0 |
| Supplemental oxygen administration (days)‡ | 43.2±40.7 | 78.6±88.8 | 83.2±81.6 | 81.8±78.4 |
| Artificial ventilation (days)§ | 13.3±22.0 | 27.6±27.7 | 24.6±16.6 | 25.3±17.5 |
| Admission to NICU (days)¶ | – | – | 92.1±58.2 | 97.2±71.1 |
↵* Column 1 vs column 2 p=0.004, 1 vs 4 p=0.004, 2 vs 3, 3 vs 4 and 2 vs 4 NS.
↵† Column 1 vs 2 NS, 1 vs 3 p=0.001, 1vs 4 p=0.003, 2 vs 3 p=0.032, 3 vs 4 NS, 2 vs 4 p=0.03.
↵‡ Column 1 vs 2 p=0.003, 1 vs 3 p=0.005, 1 vs 4 p=0.004, 2 vs 3, 3 vs 4 and 2 vs 4 NS.
↵§ Column 1 vs 2 p=0.0009, 1 vs 3 p=0.004, 1 vs 4 p=0.004, 2 vs 3, 3 vs 4 and 2 vs 4 NS.
↵¶ Column 3 vs 4 NS.
NICU, neonatal intensive care unit.