Table 3. Birth information from 22,561 singleton liveborn infants.
| Variables | Total | Maternal age at enrollment, years | P for trend | |||||||||||||||||
|
| ||||||||||||||||||||
| ≤24 | 25–29 | 30–34 | 35–39 | ≥40 | ||||||||||||||||
| n | (%, mean) | (SD) | n | (%) | n | (%) | n | (%) | n | (%) | n | (%) | ||||||||
| Gestational age at delivery, weeks | <37 | 1,474 | 6.5 | 121 | 5.7 | 340 | 5.4 | 488 | 6.0 | 367 | 7.5 | 158 | 13.7 | <0.0001 | ||||||
| 37–41 | 21,060 | 93.3 | 2,010 | 94.1 | 5,895 | 94.5 | 7,660 | 93.9 | 4,496 | 92.4 | 999 | 86.3 | <0.0001 | |||||||
| >42 | 27 | 0.1 | 4 | 0.2 | 6 | 0.1 | 12 | 0.1 | 5 | 0.1 | . | 0.36 | ||||||||
| Mean, SD | 22,309 | 38.7 | 1.8 | 2,107 | 39.0 | 1.6 | 6,181 | 38.9 | 1.7 | 8,097 | 38.7 | 1.7 | 4,842 | 38.5 | 1.9 | 1,082 | 38.3 | 2.1 | <0.0001 | |
| Birth weight | Mean, SD | 22,311 | 3,024.4 | 435.0 | 2,108 | 3,037.1 | 415.1 | 6,180 | 3,032.7 | 412.5 | 8,100 | 3,023.7 | 431.9 | 4,841 | 3,016.7 | 462.5 | 1,082 | 2,991.7 | 489.0 | 0.028 |
| Length | Mean, SD | 22,039 | 49.3 | 3.8 | 2,075 | 49.4 | 2.2 | 6,085 | 49.4 | 2.4 | 8,006 | 49.3 | 5.5 | 4,802 | 49.2 | 2.7 | 1,071 | 49.0 | 3.0 | 0.0002 |
| Head circumference | Mean, SD | 22,019 | 33.4 | 2.5 | 2,075 | 33.2 | 1.5 | 6,082 | 33.3 | 1.5 | 8,000 | 33.4 | 3.5 | 4,791 | 33.5 | 1.6 | 1,071 | 33.5 | 1.8 | <0.0001 |
| Chest circumference | Mean, SD | 21,984 | 31.8 | 2.8 | 2,070 | 31.8 | 1.8 | 6,074 | 31.9 | 1.8 | 7,989 | 31.9 | 3.8 | 4,781 | 31.9 | 2.0 | 1,070 | 31.8 | 2.4 | 0.78 |
| Sex | Male | 11,553 | 51.8 | 1,123 | 53.2 | 3,242 | 52.4 | 4,197 | 51.8 | 2,465 | 50.9 | 526 | 48.6 | 0.0052 | ||||||
| Female | 10,764 | 48.2 | 985 | 46.7 | 2,942 | 47.6 | 3,905 | 48.2 | 2,376 | 49.1 | 556 | 51.4 | 0.0050 | |||||||
| Unknown | 6 | 0.0 | 1 | 0.0 | 2 | 0.0 | 1 | 0.0 | 2 | 0.0 | . | 0.66 | ||||||||
| Placental weight | Mean, SD | 20,058 | 562.6 | 156.1 | 1,935 | 572.1 | 242.7 | 5,451 | 560.8 | 124.9 | 7,213 | 561.5 | 159.0 | 4,456 | 563.2 | 139.6 | 1,003 | 558.6 | 142.9 | 0.33 |
| Apgar score <7 at 1 min | + | 2,348 | 10.4 | 165 | 7.7 | 710 | 11.4 | 894 | 11.0 | 425 | 8.7 | 154 | 13.3 | 0.40 | ||||||
| − | 20,213 | 89.6 | 1,970 | 92.3 | 5,531 | 88.6 | 7,266 | 89.0 | 4,443 | 91.3 | 1,003 | 86.7 | ||||||||
| Apgar score <7 at 5 min | + | 2,343 | 10.4 | 181 | 8.5 | 748 | 12.0 | 905 | 11.1 | 367 | 7.5 | 142 | 12.3 | 0.016 | ||||||
| − | 20,218 | 89.6 | 1,954 | 91.5 | 5,493 | 88.0 | 7,255 | 88.9 | 4,501 | 92.5 | 1,015 | 87.7 | ||||||||
| UmA pH | Mean, SD | 17,226 | 7.31 | 0.15 | 1,696 | 7.30 | 0.17 | 4,689 | 7.31 | 0.12 | 6,128 | 7.31 | 0.15 | 3,811 | 7.31 | 0.08 | 902 | 7.29 | 0.34 | 0.47 |
| <7.00 | 45 | 0.26 | 6 | 0.36 | 12 | 0.26 | 20 | 0.33 | 3 | 0.08 | 4 | 0.44 | 0.35 | |||||||
| 7.00 to <7.20 |
1,095 | 6.36 | 118 | 6.96 | 313 | 6.68 | 360 | 5.87 | 245 | 6.43 | 59 | 6.54 | 0.38 | |||||||
| ≥7.20 | 16,086 | 93.38 | 1,572 | 92.69 | 4,364 | 93.07 | 5,748 | 93.80 | 3,563 | 93.49 | 839 | 93.02 | 0.29 | |||||||
| NICU admission | + | 1,159 | 5.1 | 96 | 4.5 | 265 | 4.2 | 409 | 5.0 | 300 | 6.2 | 89 | 7.7 | <0.0001 | ||||||
| − | 21,402 | 94.9 | 2,039 | 95.5 | 5,976 | 95.8 | 7,751 | 95.0 | 4,568 | 93.8 | 1,068 | 92.3 | ||||||||
NICU, Neonatal intensive care unit; SD, standard deviation; UmA, umbilical artery.