Maternal and pregnancy characteristics in the study population
| Characteristic | Twin pregnancy (n=16 174) | Singleton pregnancy (n=913 789) | ||
| PE, % (N) | GH, % (N) | PE, % (N) | GH, % (N) | |
| Prevalence in entire study population | 11.8 (1903) | 2.2 (357) | 3.4 (31 247) | 1.7 (15 985) |
| Maternal age, years | ||||
| <20 | 10.2 (14) | 0.7 (1) | 5.0 (1008) | 1.0 (205) |
| 20–24 | 13.4 (182) | 1.7 (23) | 4.1 (5554) | 1.3 (1807) |
| 25–29 | 12.1 (523) | 1.9 (84) | 3.4 (10 189) | 1.6 (4876) |
| 30–34 | 11.3 (706) | 2.3 (143) | 3.0 (10 189) | 1.8 (5557) |
| 35–39 | 11.1 (383) | 2.4 (84) | 3.3 (4425) | 2.1 (2864) |
| ≥40 | 14.7 (95) | 2.3 (22) | 4.1 (1017) | 2.7 (673) |
| Parity | ||||
| 0 | 16.5 (1212) | 2.7 (195) | 5.0 (19 145) | 2.2 (8615) |
| 1 | 8.4 (471) | 1.8 (100) | 2.3 (7734) | 1.4 (4568) |
| 2+ | 6.8 (220) | 1.9 (62) | 2.2 (4368) | 1.4 (2802) |
| In vitro fertilisation | 14.9 (500) | 2.6 (88) | 4.8 (890) | 2.3 (423) |
| Educational level | ||||
| None or compulsory education (gr. 0–10) | 10.0 (229) | 1.7 (39) | 3.5 (5309) | 1.3 (2008) |
| Secondary education (gr. 11–13) | 12.0 (591) | 1.8 (89) | 3.8 (10 490) | 1.8 (4806) |
| Higher education (Bachelor) | 12.5 (810) | 2.7 (174) | 3.4 (11 697) | 1.9 (6630) |
| Highest education (Master/PhD) | 11.0 (225) | 2.3 (47) | 2.7 (2944) | 2.0 (2136) |
| Missing data | 10.9 (48) | 1.8 (8) | 2.2 (807) | 1.1 (405) |
| Diabetes | ||||
| Type 1 | 35.1 (27) | 2.6 (2) | 14.6 (608) | 3.7 (152) |
| Type 2 | 20.7 (18) | 5.7 (5) | 8.5 (239) | 3.6 (101) |
| Gestational | 15.8 (46) | 3.8 (11) | 6.6 (902) | 3.0 (404) |
| Prepregnancy chronic hypertension | 40.8 (42) | NA* | 19.8 (1016) | NA* |
| Smoking | ||||
| No | 12.1 (1715) | 2.3 (329) | 3.5 (27 517) | 1.8 (14 449) |
| Sometimes | 12.0 (29) | 3.3 (8) | 3.1 (456) | 1.7 (242) |
| Daily | 9.3 (159) | 1.2 (20) | 3.1 (3274) | 1.2 (1294) |
| Body mass index (BMI, kg/m2) | ||||
| Normal and underweight, BMI <25.0 | 10.9 (235) | 1.0 (21) | 2.2 (2971) | 0.9 (1194) |
| Overweight, BMI 25.0–29.9 | 13.5 (115) | 2.2 (19) | 3.7 (1782) | 1.7 (811) |
| Obese, BMI ≥30 | 14.5 (52) | 2.8 (10) | 5.8 (1043) | 3.0 (543) |
| Missing BMI information | 11.7 (1470) | 2.4 (302) | 3.5 (24 644) | 1.9 (15 985) |
The prevalence of pre-eclampsia (PE) and gestational hypertension (GH) in the subgroups of women for each variable is presented in percentages. Number of women with PE or GH presented in brackets, n=929 963.
*NA, not applicable.