Survival and neurodevelopmental outcomes at 3 years of age for periods 1 and 2 after multiple imputations
| Total | 22 weeks | 23 weeks | 24 weeks | |||||||||||||
| Period 1 | Period 2 | Period 1 | Period 2 | Period 1 | Period 2 | Period 1 | Period 2 | |||||||||
| n=1479 | n=1839 | n=183 | n=271 | n=544 | n=686 | n=752 | n = 882 | |||||||||
| Not admitted to the NICU† | 17 | 1.1% | 43 | 2.3% | 4 | 2.2% | 26 | 9.6% | 11 | 2.0% | 13 | 1.9% | 2 | 0.3% | 4 | 0.5% |
| Death at the NICU | 471 | 31.8% | 417 | 22.7%** | 114 | 62.3% | 119 | 43.9%** | 198 | 36.4% | 169 | 24.6%** | 159 | 21.1% | 129 | 14.6%** |
| Death after discharge | 8 | 0.5% | 7 | 0.4% | 1 | 0.5% | 1 | 0.4% | 5 | 0.9% | 4 | 0.6% | 2 | 0.3% | 2 | 0.2% |
| Survived | 983 | 66.5% | 1372‡ | 74.6%** | 64 | 35.0% | 125 | 46.1%* | 330 | 60.7% | 500 | 72.9%** | 589 | 78.3% | 747‡ | 84.7%** |
| Cerebral palsy§ | 97 | 9.9% | 74 | 5.4%** | 10 | 15.6% | 10 | 8.0% | 44 | 13.3% | 28 | 5.6%** | 43 | 7.3% | 36 | 4.8%* |
| Visual impairments§ | 80 | 8.1% | 31 | 2.3%** | 4 | 6.3% | 9 | 7.2% | 33 | 10.0% | 10 | 2.0%** | 43 | 7.3% | 12 | 1.6%** |
| Hearing impairments§ | 14 | 1.4% | 6 | 0.4%* | 0 | 0.0% | 0 | 0.0% | 7 | 2.1% | 3 | 0.6% | 7 | 1.2% | 3 | 0.4% |
| DQ of KSPD < 70§ | 261 | 26.7% | 381 | 27.8% | 21 | 32.8% | 55 | 43.2% | 109 | 33.0% | 158 | 31.6% | 131 | 22.2% | 168 | 22.5% |
| NDI¶§ | 298 | 30.3% | 395 | 28.8% | 22 | 34.4% | 58 | 46.4% | 122 | 37.0% | 160 | 32.0% | 154 | 26.1% | 177 | 23.7% |
| Death or NDI¶ | 794 | 53.7% | 862 | 46.9%** | 141 | 77.0% | 204 | 75.3% | 336 | 61.8% | 346 | 50.4%** | 317 | 42.2% | 312 | 35.4%** |
*P<0.05, **P<0.01, unadjusted comparisons between periods using the χ2 or Fisher’s exact test.
†Not admitted to the NICU represents live-birth infants who were not admitted to the NICU of the same hospital and died. This category started to be registered from 2006 in period 1.
‡Two infants with missing data on death after NICU discharge in period 2 were estimated as having survived without follow-up data.
§% of each impairment represents proportion of infants with impairments among surviving infants. Unadjusted comparisons between the two periods were performed among survivors.
¶NDIs were defined as any of the following: cerebral palsy, hearing impairments, visual impairments or DQ of KSPD <70.
DQ, developmental quotient; KSPD, Kyoto Scale of Psychological Development; NDI, neurodevelopmental impairment; NICU, neonatal intensive care unit