Table 1. Characteristics of Study Cohort by Gestational Age at Birth, Sweden, 1973-1997.
| Characteristic | No. (%) | |||||
|---|---|---|---|---|---|---|
| Preterm | Early Term (37-38 wk) | Full-term (39-41 wk) | Postterm (≥42 wk) | |||
| Extremely (22-27 wk) | Very (28-33 wk) | Late (34-36 wk) | ||||
| No. (% of total) | 5391 (0.2) | 33 025 (1.3) | 110 649 (4.3) | 447 249 (17.4) | 1 742 809 (67.9) | 227 576 (8.9) |
| Child characteristics | ||||||
| Sex | ||||||
| Male | 2938 (54.5) | 18 219 (55.2) | 60 010 (54.2) | 233 117 (52.1) | 884 793 (50.8) | 119 480 (52.5) |
| Female | 2453 (45.5) | 14 806 (44.8) | 50 639 (45.8) | 214 132 (47.9) | 858 016 (49.2) | 108 096 (47.5) |
| Fetal growth percentile | ||||||
| <10th | 26 (0.5) | 3785 (11.5) | 12 127 (11.0) | 34 862 (7.8) | 159 876 (9.2) | 46 079 (20.2) |
| 10th-90th | 5115 (94.9) | 27 779 (84.1) | 89 517 (80.9) | 361 856 (80.9) | 1 402 814 (80.5) | 166 260 (73.1) |
| >90th | 250 (4.6) | 1461 (4.4) | 9005 (8.1) | 50 531 (11.3) | 180 119 (10.3) | 15 237 (6.7) |
| Multiple birth | ||||||
| Singleton | 4259 (79.0) | 26 313 (79.7) | 95 373 (86.2) | 426 617 (95.4) | 1 731 866 (99.4) | 227 034 (99.8) |
| Twin or higher order | 1132 (21.0) | 6712 (20.3) | 15 276 (13.8) | 20 632 (4.6) | 10 943 (0.6) | 542 (0.2) |
| Birth order | ||||||
| 1 | 2348 (43.5) | 14 864 (45.0) | 49 495 (44.7) | 174 039 (38.9) | 713 237 (40.9) | 109 526 (48.1) |
| 2 | 1682 (31.2) | 10 159 (30.8) | 34 364 (31.1) | 162 534 (36.3) | 656 995 (37.7) | 75 619 (33.2) |
| ≥3 | 1361 (25.3) | 8002 (24.2) | 26 790 (24.2) | 110 676 (24.8) | 372 577 (21.4) | 42 431 (18.6) |
| Maternal characteristics | ||||||
| Age, y | ||||||
| <20 | 290 (5.4) | 1867 (5.6) | 5523 (5.0) | 16 994 (3.8) | 65 154 (3.7) | 11 250 (4.9) |
| 20-29 | 2951 (54.7) | 18 690 (56.6) | 64 691 (58.5) | 261 265 (58.4) | 1 090 254 (62.6) | 147 502 (64.8) |
| 30-39 | 2015 (37.4) | 11 649 (35.3) | 37 999 (34.3) | 158 963 (35.5) | 563 886 (32.4) | 66 380 (29.2) |
| ≥40 | 135 (2.5) | 819 (2.5) | 2436 (2.2) | 10 027 (2.2) | 23 515 (1.3) | 2444 (1.1) |
| Education, y | ||||||
| <10 | 1081 (18.9) | 6179 (18.7) | 19 760 (17.9) | 73 563 (16.5) | 260 963 (15.0) | 37 651 (16.5) |
| 10-12 | 2706 (50.2) | 16 969 (51.4) | 55 632 (50.3) | 220 961 (49.4) | 855 235 (49.1) | 111 107 (48.8) |
| >12 | 1667 (30.9) | 9877 (29.9) | 35 257 (31.9) | 152 725 (34.1) | 626 611 (35.9) | 78 818 (34.6) |
| Smoking, cigarettes/d | ||||||
| 0 | 3168 (58.8) | 19 757 (59.8) | 69 298 (62.6) | 293 373 (65.6) | 1 145 634 (65.7) | 137 123 (60.3) |
| 1-9 | 1795 (33.3) | 10 628 (32.2) | 33 272 (30.1) | 123 686 (27.6) | 505 789 (29.0) | 81 573 (35.8) |
| ≥10 | 428 (7.9) | 2640 (8.0) | 8079 (7.3) | 30 190 (6.8) | 91 386 (5.2) | 8880 (3.9) |
| Preeclampsia | 420 (7.8) | 4520 (13.7) | 11 321 (10.2) | 28 430 (6.4) | 73 625 (4.2) | 10 196 (4.5) |
| Other hypertensive disorders | 45 (0.8) | 439 (1.3) | 1209 (1.1) | 4041 (0.9) | 10 517 (0.6) | 1001 (0.4) |
| Diabetes mellitus | 21 (0.4) | 267 (0.8) | 1175 (1.1) | 3059 (0.7) | 3525 (0.2) | 167 (0.1) |