Table 2.
Demographic, prenatal, and neonatal characteristics of surviving infants with and without follow-up data at 3 years of age included in the NRNJ database
| Variable | With follow-up data (n=18,110) | Without follow-up data (n=19,004) | P value |
|---|---|---|---|
| Maternal age >35 yr | 4,152/17,472 (23.8) | 4,191/18,228 (23.0) | 0.087 |
| Birth weight (g) | 1,034±294 | 1,090±288 | <0.001 |
| Birth weight distribution | |||
| <500 g | 517/18,110 (2.9) | 357/19,004 (1.9) | <0.001 |
| <1,000 g | 7615/18,110 (42.0) | 6,674/19,004 (35.1) | |
| 1,500 g | 9,978/18,110 (55.1) | 11,973/19,004 (63.0) | |
| GA (wk) | 28.9±3.1 | 29.5±3.2 | <0.001 |
| GA distribution | <0.001 | ||
| 22–27 wk | 7,002/18,110 (38.7) | 6,021/19,004 (31.7) | |
| 28–33 wk | 9,972/18,110 (55.1) | 11,218/19,004 (59) | |
| 34 wk | 1,136/18,110 (6.3) | 1,765/19,004 (9.3) | |
| Male sex | 9,273/18,110 (51.2) | 9,595/19,004 (50.5) | 0.376 |
| Multiple births | 4,468/18,110 (24.7) | 4,885/19,004 (25.7) | 0.022 |
| Life-threatening congenital anomalies | 29/17,903 (0.2) | 87/18,673 (0.5) | <0.001 |
| Non-life-threatening congenital anomalies | 702/17,903 (3.9) | 929/18,673 (5.0) | <0.001 |
| Pregnancy-related hypertension | 3,739/18,031 (20.7) | 3,706/18,649 (19.9) | 0.04 |
| Clinical CAM | 3,002/17,734 (16.9) | 2,728/17,946 (15.2) | <0.001 |
| Antenatal steroids | 8,571/17,972 (47.7) | 8,049/18,466 (43.6) | <0.001 |
| Cesarean section | 14,312/18,044 (79.3) | 14,581/18,761 (77.7) | <0.001 |
| Transferred after birth | 1,126/18,110 (6.2) | 1,698/19,004 (8.9) | <0.001 |
| RDS | 10,059/17,947 (56.0) | 9,631/18,732 (51.4) | <0.001 |
| PDA | 6,284/17,940 (35.0) | 5,901/18,733 (31.5) | <0.001 |
| CLD on day 28 | 6,502/17,484 (37.2) | 5,669/17,601 (32.2) | <0.001 |
| CLD at 36 weeks | 3,359/17,332 (19.4) | 2,838/17,358 (16.3) | <0.001 |
| NEC and/or intestinal perforation | 423/18,110 (2.3) | 479/19,004 (2.5) | 0.252 |
| Sepsis | 1,218/17,930 (6.8) | 976/18,620 (5.2) | <0.001 |
| IVH (grades 3–4) | 486/17,979 (2.7) | 594/18,650 (3.2) | 0.007 |
| Cystic periventricular leukomalacia | 556/18,022 (3.1) | 643/18,675 (3.4) | 0.056 |
| Retinopathy of prematurity, treated | 2,840/17,521 (16.2) | 2428/18,015 (13.5) | <0.001 |
| Parenteral nutrition | 11,687/18,006 (64.9) | 10,588/18,649 (56.8) | <0.001 |
| Home oxygen therapy at discharge | 962/17,937 (5.4) | 871/18,506 (4.7) | 0.004 |
Values are shown as number/number of measurements (%) or mean±standard deviation.
NRNJ, Neonatal Research Network of Japan; GA, gestational age; CAM, chorioamnionitis; RDS, respiratory distress syndrome; PDA, patent ductus arteriosus; CLD on day 28, chronic lung disease received supplemental oxygen on the 28th day after birth; CLD at 36 weeks, chronic lung disease received supplemental oxygen at 36 weeks postmenstrual age; NEC, necrotizing enterocolitis; IVH, intraventricular hemorrhage.
Boldface indicates a statistically significant difference with P<0.05.