Characteristic | Total n = 5,219,133 | Group 1 n = 690,093 | Group 2 n = 2,792,977 | Group 3 n = 1,736,063 | P-values a |
---|---|---|---|---|---|
Maternal age, y (n, %) | |||||
16 ∽ 24 | 1,074,234 (20.58) | 88,041 (12.76) | 577,940 (20.69) | 408,253 (23.52) | < 0.001 A, B, C |
25 ∽ 29 | 1,970,479 (37.75) | 256,200 (37.13) | 1,092,518 (39.12) | 621,761 (35.81) | |
30 ∽ 34 | 1,447,580 (27.74) | 224,487(32.53) | 739,376(26.47) | 483,717(27.86) | |
35 ∽ 39 | 593,765 (11.38) | 97,621(14.15) | 315,716(11.30) | 180,428(10.39) | |
40 ∽ 50 | 127,682 (2.45) | 23,421 (3.39) | 65,683 (2.35) | 38,578 (2.22) | |
< 16 or missing data | 5393 (0.10) | 323 (0.05) | 1744 (0.06) | 3326 (0.19) | |
Infant sex (n, %) | |||||
male | 2,792,678 (53.51) | 368,491 (53.39) | 1,495,098 (53.53) | 929,089 (53.52) | < 0.001 A, B, C |
female | 2,425,934 (46.48) | 321,567 (46.60) | 1,297,607 (46.46) | 806,760 (46.47) | |
Unknown | 521 (0.01) | 35 (0.01) | 272 (0.01) | 214 (0.01) | |
Delivery mode (n, %) | |||||
Vaginal delivery | 3,535,799 (67.75) | 447,506 (64.85) | 1,947,974 (69.75) | 1,140,319 (65.68) | < 0.001 A, B, C |
Cesarean | 1,683,334 (32.25) | 242,587 (35.15) | 845,003 (30.25) | 595,744 (34.32) | |
Birth Season (n, %) | |||||
Spring | 1,175,442 (22.52) | 163,745 (23.73) | 630,546 (22.58) | 381,151 (21.96) | < 0.001 A, B, C |
Summer | 1,364,830 (26.15) | 173,388 (25.13) | 715,175 (25.61) | 476,267 (27.43) | |
Autumn | 1,496,777 (28.68) | 183,662 (26.61) | 804,837 (28.81) | 508,278 (29.28) | |
Winter | 1,182,084(22.65) | 169,298 (24.53) | 642,419 (23.00) | 370,367 (21.33) | |
Mean gestational age mean ± SD (wk) | 38.74 ± 1.50 | 38.59 ± 1.50 | 38.73 ± 1.49 | 38.81 ± 1.51 | < 0.001 A, B, C |
Mean birth weight mean ± SD (g) | 3180.01 ± 440.70 | 3160.02 ± 439.31 | 3151.45 ± 432.63 | 3233.89 ± 449.08 | < 0.001 A, B, C |