Table 1.
Baseline maternal characteristics by ever occurrence of preterm delivery or hypertensive disorders of pregnancy, Sweden, 1973–2015.
| Characteristic | All women | Preterm deliverya | Hypertensive disorders of pregnancya |
|---|---|---|---|
| N=2,184,417 | N=199,888 | N=138,927 | |
| n (%) | n (%) | n (%) | |
| Age at first delivery (years) | |||
| <20 | 119,710 (5.5) | 17,020 (8.5) | 7,241 (5.2) |
| 20–24 | 601,766 (27.5) | 60,146 (30.1) | 37,105 (26.7) |
| 25–29 | 786,853 (36.0) | 66,337 (33.2) | 47,240 (34.0) |
| 30–34 | 479,158 (21.9) | 39,226 (19.6) | 30,752 (22.1) |
| 35–39 | 163,858 (7.5) | 14,085 (7.1) | 13,099 (9.4) |
| ≥40 | 33,072 (1.5) | 3,074 (1.5) | 3,490 (2.5) |
| Year of first delivery | |||
| 1973–1979 | 528,377 (24.2) | 43,883 (22.0) | 46,226 (33.3) |
| 1980–1989 | 442,789 (20.3) | 48,069 (24.0) | 28,329 (20.4) |
| 1990–1999 | 443,023 (20.3) | 44,036 (22.0) | 22,802 (16.4) |
| 2000–2009 | 457,198 (20.9) | 41,729 (20.9) | 23,479 (16.9) |
| 2010–2015 | 313,030 (14.3) | 22,171 (11.1) | 18,091 (13.0) |
| Education (years) | |||
| ≤9 | 304,146 (13.9) | 31,017 (15.5) | 21,428 (15.4) |
| 10–12 | 966,928 (44.3) | 93,528 (46.8) | 64,892 (46.7) |
| >12 | 913,343 (41.8) | 75,343 (37.7) | 52,607 (37.9) |
| Employed | 1,885,274 (86.3) | 170,335 (85.2) | 125,272 (90.2) |
| Income (quartile) | |||
| 1st (highest) | 545,763 (25.0) | 44,716 (22.4) | 32,128 (23.1) |
| 2nd | 546,304 (25.0) | 47,629 (23.8) | 34,959 (25.2) |
| 3rd | 547,162 (25.0) | 50,435 (25.2) | 38,039 (27.4) |
| 4th (lowest) | 545,188 (25.0) | 57,118 (28.6) | 33,801 (24.3) |
| Country of origin | |||
| Sweden | 1,792,242 (82.0) | 164,900 (82.5) | 119,741 (86.2) |
| Other European | 205,457 (9.4) | 17,542 (8.8) | 12,211 (8.8) |
| Non-European | 186,718 (8.5) | 17,446 (8.7) | 6,975 (5.0) |
| Body mass index (kg/m 2 ) | |||
| <18.5 | 52,751 (2.4) | 5,928 (3.0) | 1,670 (1.2) |
| 18.5–24.9 | 839,921 (38.5) | 71,149 (35.6) | 36,714 (26.4) |
| 25.0–29.9 | 241,515 (11.1) | 21,112 (10.6) | 17,790 (12.8) |
| ≥30.0 | 90,965 (4.2) | 9,205 (4.6) | 11,064 (8.0) |
| Unknown | 959,265 (43.9) | 92,494 (46.2) | 71,689 (51.6) |
| Smoking (cigarettes/day) | |||
| 0 | 1,244,022 (56.9) | 108,621 (54.3) | 70,227 (50.6) |
| 1–9 | 152,835 (7.0) | 16,539 (8.3) | 6,990 (5.0) |
| ≥10 | 68,358 (3.1) | 8,672 (4.3) | 2,961 (2.1) |
| Unknown | 719,202 (32.9) | 66,056 (33.0) | 58,749 (42.3) |
| Prior diagnoses | |||
| Hypertension | 1,739 (0.1) | 365 (0.2) | 927 (0.7) |
| Hyperlipidemia | 1,332 (0.1) | 155 (0.1) | 144 (0.1) |
| Gestational diabetes | 9,412 (0.4) | 1,394 (0.7) | 1,201 (0.9) |
| Infant birth weight for gestational age (percentile) | |||
| <10th | 218,442 (10.0) | 25,279 (12.6) | 22,709 (16.3) |
| 10th to 90th | 1,747,534 (90.0) | 162,714 (81.4) | 104,520 (75.2) |
| ≥90th | 218,441 (10.0) | 11,895 (6.0) | 11,698 (8.4) |
a
All characteristics differed significantly compared to women without the respective adverse pregnancy outcome (P<0.05) using the Kruskal-Wallis test for equality of populations.