Table 1 Background characteristics of 12 002 women of the Northern Finland 1966 Birth Cohort according to parity.
| Final parity | |||||
|---|---|---|---|---|---|
| 1 (n = 746) | 2–4 (n = 7913) | 5–9 (n = 2825) | ⩾10 (n = 518) | p Value* | |
| Age at menarche† | 13.6 (1.6) | 13.9 (1.4) | 14.4 (1.4) | 14.2 (1.5) | <0.001 |
| Age at first birth† | 24.0 (5.3) | 22.8 (3.8) | 22.4 (3.4) | 22.2 (2.8) | <0.001 |
| Age in 1966† | 24.0 (5.3) | 26.1 (5.6) | 32.2 (6.5) | 35.2 (7.1) | <0.001 |
| Age at death† | 50.1 (12.0) | 53.9 (10.9) | 60.2 (11.2) | 65.6 (9.3) | <0.001 |
| Age in 2001† | 59.4 (5.0) | 61.4 (5.5) | 67.2 (6.3) | 69.6 (7.2) | <0.001 |
| Socioeconomic position in 1966 (%) | <0.001 | ||||
| White collar | 19.8 | 26.4 | 16.2 | 13.3 | |
| Blue collar | 42.8 | 37.1 | 22.2 | 17.2 | |
| Unskilled workers | 26.1 | 22.7 | 26.8 | 19.5 | |
| Farmers | 8.2 | 12.2 | 33.9 | 49.0 | |
| Missing | 3.1 | 1.6 | 0.8 | 1.0 | |
| Pre‐pregnancy BMI in 1966 (%) | <0.001 | ||||
| <25.0 | 80.4 | 76.5 | 56.7 | 46.5 | |
| 25.0–29.9 | 9.4 | 14.1 | 23.5 | 28.4 | |
| ⩾30.0 | 0.9 | 2.0 | 7.2 | 10.2 | |
| Missing | 9.2 | 7.5 | 12.5 | 14.9 | |
| Smoking before pregnancy in 1966 (%) | <0.001 | ||||
| No | 63.8 | 74.5 | 81.4 | 87.8 | |
| Yes | 33.8 | 23.1 | 15.9 | 10.8 | |
| Missing | 2.4 | 2.4 | 2.7 | 1.4 | |
| Parity in 1966 (%) | <0.001 | ||||
| 1 | 100.0 | 36.7 | 7.1 | 6.6 | |
| 2–4 | 62.4 | 29.2 | 14.3 | ||
| 5–9 | 0 | 62.9 | 32.1 | ||
| ⩾10 | 0 | 0 | 45.2 | ||
| Missing data in 1966 | 0.8 | 0.8 | 1.9 | ||
BMI, body mass index.
*Student t test for continuous variables, χ2 test for categorical variables.
†Age represented in years, as mean (SD).