Table 1.
Characteristics of study participants by shortest pregnancy duration, Sweden, 1973-2015.
| Extremely preterm |
Very preterm |
Late preterm | Early term | Full-term | Post-term | |
|---|---|---|---|---|---|---|
| (22-27 wks) | (28-33 wks) | (34-36 wks) | (37-38 wks) | (39-41 wks) | (≥42 wks) | |
| N=9,075 | N=45,372 | N=140,096 | N=551,190 | N=1,352,785 | N=89,525 | |
| n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | |
| Age at first delivery (yrs) | ||||||
| <20 | 801 (8.8) | 4,119 (9.1) | 11,396 (8.1) | 35,932 (6.5) | 64,194 (4.7) | 2,811 (3.1) |
| 20-24 | 2,577 (28.4) | 13,312 (29.3) | 42,360 (30.2) | 162,194 (29.4) | 364,022 (26.9) | 17,765 (19.8) |
| 25-29 | 2,773 (30.6) | 14,573 (32.1) | 47,238 (33.7) | 194,425 (35.3) | 498,447 (36.9) | 31,067 (34.7) |
| 30-34 | 1,863 (20.5) | 9,026 (19.9) | 27,426 (19.6) | 112,679 (20.4) | 304,617 (22.5) | 24,752 (27.7) |
| 35-39 | 853 (9.4) | 3,491 (7.7) | 9,633 (6.9) | 37,728 (6.8) | 101,714 (7.5) | 11,036 (12.3) |
| ≥40 | 208 (2.3) | 851 (1.9) | 2,043 (1.5) | 8,232 (1.5) | 19,791 (1.5) | 2,094 (2.3) |
| Year of delivery | ||||||
| 1973-1979 | 1,441 (15.9) | 10,126 (22.3) | 31,063 (22.2) | 112,398 (20.4) | 338,090 (25.0) | 33,926 (37.9) |
| 1980-1989 | 1,768 (19.5) | 10,744 (23.7) | 33,757 (24.1) | 126,282 (22.9) | 258,759 (19.1) | 11,881 (13.3) |
| 1990-1999 | 1,989 (21.9) | 9,991 (22.0) | 30,400 (21.7) | 121,582 (22.1) | 267,573 (19.8) | 12,213 (13.6) |
| 2000-2009 | 2,235 (24.6) | 9,316 (20.5) | 29,125 (20.8) | 126,296 (22.9) | 279,102 (20.6) | 12,959 (14.5) |
| 2010-2015 | 1,642 (18.1) | 5,195 (11.5) | 15,751 (11.2) | 64,632 (11.7) | 209,261 (15.5) | 18,546 (20.7) |
| Final parity | ||||||
| 1 | 1,721 (19.0) | 8,341 (18.4) | 23,542 (16.8) | 86,218 (15.6) | 326,697 (24.1) | 46,414 (51.8) |
| 2 | 3,067 (33.8) | 18,055 (39.8) | 62,467 (44.6) | 263,178 (47.8) | 669,391 (49.5) | 29,673 (33.1) |
| 3 | 2,489 (27.4) | 11,435 (25.2) | 34,726 (24.8) | 140,213 (25.4) | 269,983 (19.9) | 9,981 (11.2) |
| 4 | 1,125 (12.4) | 4,737 (10.4) | 12,654 (9.0) | 42,689 (7.7) | 64,246 (4.8) | 2,431 (2.7) |
| ≥5 | 673 (7.4) | 2,804 (6.2) | 6,707 (4.8) | 18,892 (3.4) | 23,468 (1.7) | 1,026 (1.2) |
| Education (years) | ||||||
| ≤9 | 1,502 (16.6) | 7,483 (16.5) | 21,378 (15.3) | 75,746 (13.7) | 181,787 (13.4) | 16,090 (18.0) |
| 10-12 | 4,205 (46.3) | 21,490 (47.4) | 65,383 (46.7) | 247,462 (44.9) | 591,170 (43.7) | 38,787 (43.3) |
| >12 | 3,368 (37.1) | 16,399 (36.1) | 53,335 (38.1) | 227,982 (41.4) | 579,828 (42.9) | 34,648 (38.7) |
| Employment | 7,505 (82.7) | 38,225 (84.3) | 119,958 (85.6) | 474,304 (86.1) | 1,173,294 (86.7) | 75,529 (84.4) |
| Income (quartile) | ||||||
| 1st (highest) | 2,484 (27.4) | 10,373 (22.9) | 31,217 (22.3) | 130,963 (23.8) | 348,660 (25.8) | 24,437 (27.3) |
| 2nd | 2,222 (24.5) | 10,706 (23.6) | 33,539 (23.9) | 132,154 (24.0) | 341,908 (25.3) | 25,365 (28.3) |
| 3rd | 1,907 (21.0) | 11,589 (25.5) | 35,866 (25.6) | 138,437 (25.1) | 338,948 (25.1) | 22,461 (25.1) |
| 4th (lowest) | 2,462 (27.1) | 12,704 (28.0) | 39,474 (28.2) | 149,636 (27.1) | 323,269 (23.9) | 17,262 (19.3) |
| Birth country or region | ||||||
| Sweden | 6,931 (76.4) | 37,376 (82.4) | 116,167 (82.9) | 448,987 (81.5) | 1,114,195 (82.4) | 72,319 (80.8) |
| Other Europe/US/Canada | 962 (10.6) | 3,973 (8.8) | 12,122 (8.7) | 48,814 (8.9) | 128,965 (9.5) | 10,418 (11.6) |
| Asia/Oceania | 741 (8.2) | 2,667 (5.9) | 8,353 (6.0) | 38,223 (6.9) | 73,880 (5.5) | 3,703 (4.1) |
| Africa | 325 (3.6) | 897 (2.0) | 1,927 (1.4) | 8,145 (1.5) | 21,724 (1.6) | 2,208 (2.5) |
| Latin America | 106 (1.2) | 399 (0.9) | 1,388 (1.0) | 6,479 (1.2) | 12,653 (0.9) | 757 (0.9) |
| Other/unknown | 9 (0.1) | 60 (0.1) | 139 (1.0) | 542 (0.1) | 1,368 (0.1) | 120 (0.1) |
| Smoking (cigarettes/day) | ||||||
| 0 | 6,580 (72.5) | 31,195 (68.8) | 99,772 (71.2) | 409,890 (74.4) | 992,541 (73.4) | 57,918 (64.7) |
| 1-9 | 2,057 (22.7) | 12,020 (26.5) | 34,509 (24.6) | 121,431 (22.0) | 321,887 (23.8) | 29,578 (33.0) |
| ≥10 | 438 (4.8) | 2,157 (4.7) | 5,815 (4.2) | 19,869 (3.6) | 38,357 (2.8) | 2,029 (2.3) |
| Body mass index (kg/m2) | ||||||
| <18.5 | 218 (2.4) | 1,290 (2.8) | 4,209 (3.0) | 16,221 (2.9) | 29,729 (2.2) | 1,048 (1.2) |
| 18.5-24.9 | 6,908 (76.1) | 36,644 (80.8) | 113,938 (81.3) | 450,033 (81.7) | 1,109,729 (82.0) | 72,138 (80.6) |
| 25.0-29.9 | 1,342 (14.8) | 5,162 (11.4) | 15,652 (11.2) | 62,437 (11.3) | 158,184 (11.7) | 11,217 (12.5) |
| ≥30.0 | 607 (6.7) | 2,276 (5.0) | 6,297 (4.5) | 22,499 (4.1) | 55,143 (4.1) | 5,122 (5.7) |
| Preeclampsia | 1,023 (11.3) | 6,979 (15.4) | 14,148 (10.1) | 35,673 (6.5) | 61,296 (4.5) | 4,099 (4.6) |
| Other hypertensive disorders | 102 (1.1) | 679 (1.5) | 1,750 (1.3) | 6,226 (1.1) | 12,600 (0.9) | 738 (0.8) |
| Diabetes mellitus | 213 (2.3) | 1,389 (3.1) | 4,315 (3.1) | 9,985 (1.8) | 11,098 (0.8) | 477 (0.5) |