Table 1.
Characteristics of participants by gestational age at birth, Sweden, 1973-2014
| Characteristics | Extremely preterm (22-27 weeks) | Very preterm (28-33 weeks) | Late preterm (34-36 weeks) | Early term (37-38 weeks) | Full term (39-41 weeks) | Post-term (≥42 weeks) |
|---|---|---|---|---|---|---|
| No of participants | 8129 | 43 516 | 155 626 | 737 412 | 2 895 746 | 346 186 |
| Child characteristics | ||||||
| Sex: | ||||||
| Male | 4435 (54.6) | 24 286 (55.8) | 84 696 (54.4) | 379 645 (51.5) | 1 471 045 (50.8) | 188 354 (54.4) |
| Female | 3694 (45.4) | 19 230 (44.2) | 70 930 (45.6) | 357 767 (48.5) | 1 424 701 (49.2) | 157 832 (45.6) |
| Birth order: | ||||||
| 1 | 4094 (50.4) | 22 513 (51.7) | 77 533 (49.8) | 296 887 (40.3) | 1 218 861 (42.1) | 172 698 (49.9) |
| 2 | 2292 (28.2) | 12 211 (28.1) | 46 346 (29.8) | 269 837 (36.6) | 1 087 327 (37.5) | 111 056 (32.1) |
| ≥3 | 1743 (21.4) | 8792 (20.2) | 31 747 (20.4) | 170 688 (23.1) | 589 558 (20.4) | 62 432 (18.0) |
| Congenital anomalies | 219 (2.7) | 1115 (2.6) | 1775 (1.1) | 2733 (0.4) | 5024 (0.2) | 944 (0.3) |
| Maternal characteristics | ||||||
| Age (years): | ||||||
| <20 | 356 (4.4) | 2056 (4.7) | 6464 (4.2) | 22 060 (3.0) | 84 018 (2.9) | 12 962 (3.7) |
| 20-24 | 1554 (19.1) | 8868 (20.4) | 33 037 (21.2) | 138 918 (18.8) | 580 804 (20.1) | 76 288 (22.0) |
| 25-29 | 2378 (29.3) | 13 488 (31.0) | 50 748 (32.6) | 242 523 (32.9) | 1 018 704 (35.2) | 121 282 (35.0) |
| 30-34 | 2206 (27.1) | 11 552 (26.6) | 40 970 (26.3) | 210 743 (28.6) | 821 392 (28.4) | 92 811 (26.8) |
| 35-39 | 1280 (15.7) | 6012 (13.8) | 19 826 (12.7) | 100 289 (13.6) | 330 684 (11.4) | 36 880 (10.7) |
| ≥40 | 355 (4.4) | 1540 (3.5) | 4581 (2.9) | 22 879 (3.1) | 60 144 (2.1) | 5963 (1.7) |
| Education (years): | ||||||
| <10 | 1369 (16.8) | 7229 (16.6) | 24 216 (15.6) | 103 813 (14.1) | 367 744 (12.7) | 48 593 (14.0) |
| 10-12 | 3867 (47.6) | 20 812 (47.8) | 73 689 (47.3) | 337 757 (45.8) | 1 304 617 (45.1) | 157 016 (45.4) |
| >12 | 2893 (35.6) | 15 475 (35.6) | 57 721 (37.1) | 295 842 (40.1) | 1 223 385 (42.2) | 140 577 (40.6) |
| Body mass index: | ||||||
| <18.5 | 137 (1.7) | 1118 (2.6) | 4767 (3.1) | 21 727 (2.9) | 65 593 (2.3) | 4649 (1.3) |
| 18.5-24.9 | 6006 (73.9) | 33 733 (77.5) | 120 397 (77.4) | 565 433 (76.7) | 2 279 136 (78.7) | 275 210 (79.5) |
| 25.0-29.9 | 1381 (17.0) | 5935 (13.6) | 21 157 (13.6) | 107 005 (14.5) | 404 104 (14.0) | 46 599 (13.5) |
| ≥30.0 | 605 (7.4) | 2730 (6.3) | 9305 (6.0) | 43 247 (5.9) | 146 913 (5.1) | 19 728 (5.7) |
| Smoking (cigarettes/day): | ||||||
| 0 | 5904 (72.6) | 30 588 (70.3) | 113 066 (72.6) | 562 247 (76.3) | 2 215 716 (76.5) | 247 294 (71.4) |
| 1-9 | 1731 (21.3) | 10 181 (23.4) | 33 600 (21.6) | 138 227 (18.7) | 567 319 (19.6) | 87 933 (25.4) |
| ≥10 | 494 (6.1) | 2747 (6.3) | 8960 (5.8) | 36 938 (5.0) | 112 711 (3.9) | 10 959 (3.2) |
| Pre-eclampsia | 1027 (12.6) | 7775 (17.8) | 15 822 (10.2) | 39 087 (5.3) | 94 678 (3.3) | 11 831 (3.4) |
| Other hypertensive disorders | 111 (1.4) | 767 (1.8) | 2191 (1.4) | 8806 (1.2) | 24 736 (0.9) | 2347 (0.7) |
| Diabetes mellitus | 88 (1.1) | 902 (2.1) | 3867 (2.5) | 11 940 (1.6) | 16 748 (0.6) | 710 (0.2) |