Table 1.
Descriptive characteristics of the study population
| Characteristics | Nulliparous (n = 1925) | Parous (n = 21,513) |
|---|---|---|
| Birthyear, median (IQR) | 1958 (1949–1966) | 1958 (1951–1965) |
| Ever smoked daily, n (%) | ||
| No | 924 (48) | 8500 (40) |
| Yes | 1001 (52) | 13,013 (60) |
| Education, n (%) | ||
| Lower secondary | 437 (23) | 3823 (18) |
| Upper secondary | 814 (42) | 10,061 (47) |
| Tertiary | 674 (35) | 7629 (35) |
| Ever used oral contraceptives, n (%)* | ||
| No | 693 (36) | 4380 (20) |
| Yes | 708 (37) | 13,077 (61) |
| Missing | 524 (27) | 4056 (19) |
| Ever used blood pressure medication, n (%) | ||
| No | 1721 (89) | 19,075 (89) |
| Yes | 204 (11) | 2434 (11) |
| Missing | 0 (0) | 4 (0) |
| Births, n (%) | ||
| 1 | N/A | 2577 (12) |
| 2 | N/A | 9778 (46) |
| 3 or more | N/A | 9158 (42) |
| Age at 1st birth, median (IQR) | N/A | 23 (20–26) |
| Year of 1st birth, median (IQR) | N/A | 1981 (1973–1990) |
| Breastfeeding length of first child, n (%)* | ||
| No breastfeeding | N/A | 994 (5) |
| < 3 months | N/A | 2864 (13) |
| 3–6 months | N/A | 5437 (25) |
| > 6 months | N/A | 7401 (34) |
| Missing | N/A | 4817 (22) |
| No. of HUNT exams, n (%) | ||
| 1 | 898 (47) | 7307 (34) |
| 2 | 562 (29) | 7022 (33) |
| 3 | 465 (24) | 7184 (33) |
| Time varying covariates | ||
| Number of observations, n (%) | 3417 (7) | 42,903 (93) |
| BMI at HUNT exam, kg/m2 | ||
| < 25 | 1792 (52) | 24,022 (56) |
| 25–29.9 | 953 (28) | 12,935 (30) |
| ≥ 30 | 648 (19) | 5881 (14) |
| Missing | 24 (1) | 65 (0.2) |
| Current use of oral contraceptives, n (%)* | ||
| No | 1684 (49) | 22,686 (53) |
| Yes | 234 (7) | 2797 (7) |
| Missing | 1499 (44) | 17,420 (41) |
| Current use of blood pressure medication, n (%) | ||
| No | 3192 (93) | 40,461 (94) |
| Yes | 219 (6) | 2338 (6) |
| Missing | 6 (0.2) | 104 (0.2) |
*Queried at HUNT2 and HUNT3