Table 1 Background characteristics of the study population including Chi-2-test comparing ‘Small ΔpH’ (10th percentile ≤0.02) and ‘Large ΔpH’ (90th percentile ≥0.15)
N | % | Small ΔpHa ≤ 0.02 | Large ΔpH ≥0.15 | Chi-2-test | |||
|---|---|---|---|---|---|---|---|
N | % | N | % | P-value | |||
Total N | 108,629 | 100 | 12,015 | 100 | 12,261 | 100 | |
Maternal age in years | 0.028 | ||||||
< 20 | 2053 | 1.9 | 229 | 1.9 | 184 | 1.5 | |
20–34 | 85,681 | 78.9 | 9543 | 79.4 | 9671 | 78.9 | |
35–39 | 17,552 | 16.2 | 1904 | 15.8 | 2050 | 16.7 | |
40+ | 3343 | 3.1 | 339 | 2.8 | 356 | 2.9 | |
Parity | < 0.000 | ||||||
Primipara | 50,116 | 46.1 | 5867 | 49.2 | 5159 | 42.6 | |
Multipara | 57,372 | 52,8 | 6054 | 50.8 | 6960 | 57.4 | |
Multipara with previous CSb | 5464 | 5.0 | – | – | – | – | |
Missing | 1141 | 1.1 | – | – | – | – | |
Maternal BMIc | 0.005 | ||||||
< 18.5 | 149 | 0.1 | 25 | 3.4 | 11 | 1.6 | |
18.5–24.9 | 3433 | 3.2 | 384 | 51.7 | 306 | 45.7 | |
25–29.9 | 2221 | 2.0 | 247 | 33.2 | 243 | 36.3 | |
30+ | 885 | 0.8 | 87 | 11.7 | 109 | 16.3 | |
Missing data | 101,941 | 93.8 | – | – | – | – | |
Maternal smoking | < 0.000 | ||||||
No | 70,714 | 65.1 | 8099 | 91.5 | 7898 | 93.6 | |
Yes 1–9 cigarettes/day | 4635 | 4.3 | 551 | 6.2 | 400 | 5.5 | |
Yes, ≥10 cigarettes/day | 1718 | 1.6 | 119 | 2.2 | 139 | 2.0 | |
Missing data | 31,562 | 29.1 | – | – | – | – | |
Birth start | < 0.000 | ||||||
Spontaneous | 91,017 | 83.8 | 10,020 | 83.4 | 10,885 | 88.8 | |
Induction | 10,379 | 9.6 | 1183 | 9.9 | 1242 | 10.1 | |
CS | 7214 | 6.6 | 807 | 6.7 | 132 | 1.1 | |
Missing data | 19 | 0.0 | – | – | – | – | |
Birth mode | < 0.000 | ||||||
Vaginal, non-instrumental | 85,196 | 78.4 | 9052 | 75.9 | 10,636 | 87.7 | |
Elective CS | 6623 | 6.1 | 713 | 6.0 | 118 | 1.0 | |
Emergency CS | 7785 | 7.2 | 1167 | 9.8 | 112 | 0.9 | |
Immediate emergency CS | 791 | 0.7 | 155 | 1.3 | 43 | 0.4 | |
Instrumental (VEd/forceps) | 7407 | 6.8 | 837 | 7.0 | 1215 | 10.0 | |
Missing | 827 | 0.8 | – | – | – | – | |
Gestational duration in weeks (days) | < 0.000 | ||||||
37 + 0–40 + 6 (259–286) | 80,716 | 74.3 | 9117 | 75.9 | 8780 | 71.6 | |
41 + 0–41 + 6 (287–293) | 20,072 | 18.5 | 2038 | 17.0 | 2531 | 20.6 | |
> 42 + 0 (294+) | 7841 | 7.2 | 860 | 7.2 | 950 | 7.7 | |
Sex | 0.132 | ||||||
Male | 56,300 | 51.8 | 6148 | 51.2 | 6432 | 52.5 | |
Female | 52,244 | 48.1 | 5855 | 48.7 | 5817 | 47.4 | |
Missing | 85 | 0.1 | 12 | 0.1 | 12 | 0.1 | |
Birthweight (g) | < 0.000 | ||||||
< 2500 | 931 | 0.9 | 177 | 1.5 | 26 | 0.2 | |
2500–3999 | 85,612 | 78.8 | 9731 | 81.0 | 8880 | 72.4 | |
4000–4499 | 17,569 | 16.2 | 1703 | 14.2 | 2647 | 21.6 | |
4500+ | 4463 | 4.1 | 397 | 3.3 | 706 | 5.8 | |
Missing data | 54 | 0.0 | – | – | – | – | |
Apgar score at 5 minutes | 0.001 | ||||||
0–3 | 95 | 0.1 | 9 | 0.1 | 21 | 0.2 | |
4–6 | 863 | 0.8 | 109 | 0.9 | 161 | 1.3 | |
7–10 | 107,652 | 99.1 | 11,895 | 99.0 | 12,078 | 98.5 | |
Missing data | 19 | 0.0 | – | – | – | – | |