Table 2.
Multivariate logistic analysis of risk factors for preterm delivery in Denmark, 1995-2004
|
All preterm
|
Extremely preterm*
|
Very preterm*
|
Moderately preterm*
|
||||||
|---|---|---|---|---|---|---|---|---|---|
| No | Odds ratio (95% CI) | No | Odds ratio (95% CI) | No | Odds ratio (95% CI) | No | Odds ratio (95% CI) | ||
| Mode of conception: | |||||||||
| Spontaneous | 63 0928 | 34 039 | 1.00 | 1379 | 1.00 | 3607 | 1.00 | 29 053 | 1.00 |
| In vitro fertilisation | 15 216 | 2 711 | 1.25 (1.19 to 1.32) | 197 | 1.76 (1.47 to 2.12) | 345 | 1.15 (1.01 to 1.31) | 2 169 | 1.17 (1.10 to 1.24) |
| Initiation of delivery: | |||||||||
| Spontaneous | 55 7267 | 29 870 | 1.00 | 1433 | 1.00 | 3344 | 1.00 | 25 093 | 1.00 |
| Elective | 88 877 | 6 880 | 1.09 (1.06 to 1.12) | 143 | 0.39 (0.33 to 0.46) | 608 | 0.77 (0.71 to 0.85) | 6 129 | 1.19 (1.15 to 1.23) |
| Parity: | |||||||||
| Primiparous | 28 7080 | 19 938 | 1.53 (1.49 to 1.57) | 931 | 1.79 (1.60 to 1.99) | 2240 | 1.63 (1.52 to 1.74) | 16 767 | 1.48 (1.44 to 1.51) |
| Multiparous | 35 9064 | 16 812 | 1.00 | 645 | 1.00 | 1712 | 1.00 | 14 455 | 1.00 |
| Type of pregnancy: | |||||||||
| Singleton | 633 012 | 30 859 | 1.00 | 1250 | 1.00 | 3171 | 1.00 | 26 438 | 1.00 |
| Multiple | 13 132 | 5 891 | 14.03 (13.75 to 14.90) | 326 | 11.12 (9.6 to 12.87) | 781 | 11.88 (10.83 to 13.02) | 4 784 | 11.70 (11.22 to 12.20) |
| Maternal age† | 646 144 | 36 750 | 1.01 (1.01 to 1.01) | 1576 | 1.03 (1.02 to 1.04) | 3952 | 1.02 (1.01 to 1.02) | 31 222 | 1.01 (1.01 to 1.01) |
| Year‡ | 646 144 | 36 750 | 1.03 (1.02 to 1.03) | 1576 | 1.06 (1.04 to 1.07) | 3952 | 1.03 (1.01 to 1.04) | 31 222 | 1.02 (1.02 to 1.03) |
| Smoking: | |||||||||
| Non-smoker | 489 129 | 24 820 | 1.00 | 916 | 1.00 | 2479 | 1.00 | 21 425 | 1.00 |
| Smoker | 131 914 | 9 190 | 1.52 (1.49 to 1.55) | 379 | 2.26 (2.11 to 2.42) | 1041 | 1.76 (1.68 to 1.85) | 7 770 | 1.41 (1.38 to 1.44) |
| Ethnic origin: | |||||||||
| White European | 608 339 | 34 778 | 0.93 (0.88 to 0.97) | 1493 | 0.86 (0.69 to 1.07) | 3751 | 0.94 (0.81 to 1.09) | 29 534 | 0.94 (0.89 to 0.98) |
| Other | 37 797 | 1 972 | 1.00 | 83 | 1.00 | 201 | 1.00 | 1 688 | 1.00 |
CI, confidence interval.
All odds ratios were mutually adjusted for other variables in the table.
*
Extremely preterm: 22-27 completed weeks of gestation; very preterm: 28-31; moderately preterm: 32-36; term: ≥37.
†
Odds ratio for a one year change in age.
‡
Odds ratio for a one year change in calendar time.