Table 1 Characteristics of all preterm infants [mean ± SD or n(%)]
Characteristics | Total (n = 10,624) |
|---|---|
Male, n (%) | 5895 (55.5) |
Primiparity, n (%) | 5955 (56.1) |
Gestational age, weeks | 35.0 ± 1.8 |
Birth weight, g | 2463 ± 520 |
Birth weight z-scorea | 0.04 ± 0.91 |
Caesarean section, n (%) | 6376 (60.0) |
Maternal age, years | 29.7 ± 4.9 |
Paternal age, years | 31.7 ± 5.9 |
≥ college (maternal education) | 6945 (76.6) |
≥ college (paternal education) | 7102 (78.3) |
Subgroup by gestational age | |
  < 28 weeks, n (%) | 40 (0.4) |
 28 ~ 31+ 6 weeks, n (%) | 642 (6.0) |
 32 ~ 33+ 6 weeks, n (%) | 1161 (10.9) |
 34 ~ 36+ 6 weeks, n (%) | 8781 (82.7) |
Subgroup by birth weight | |
  < 1000 g, n (%) | 35 (0.3) |
 1000-1499 g, n (%) | 437 (4.1) |
 1500 ~ 2499 g, n (%) | 4810 (45.3) |
  > 2500 g, n (%) | 5342 (50.3) |
Intrauterine growth status | |
 SGA, n (%) | 681 (6.4) |
 AGA, n (%) | 9141 (86.0) |
 LGA, n (%) | 802 (7.6) |