Table 1 Population description

Birth year, range

1954–1993

1938–1990

1952–1988

1952–1988

Highest obtained parity (1st–3rd quartile; range)

2 (2–3) [range: 1–14]

2 (2–3) [range: 1–14]

2 (2–3) [range: 1–10]

2 (2–3) [range: 1–10]

Participants in pregnancies with more than one different partner, n (%)

9147 (13.3%)

5819 (12.3%)

745 (4.74%)

178 (2.08%)

Age in first pregnancy, median (1st–3rd quartile)

27 (24–30)

29 (26–33)

24 (20–27)

26 (23–29)

Education years, mean ± SD

17.0 ± 3.36

16.3 ± 3.56

14.3 ± 4.13

13.5 ± 4.08

Body mass index (kg/m²), median (1st–3rd quartile)

23.1 (21.1–25.9)

25.4 (23.6–27.7)

25.2 (22.7–28.6)

26.6 (24.5–29.1)

Ever smokers, n (%)

35,631 (52.3%)

24,294 (51.2%)

8,865 (57.0%)

4,233 (50.1%)

Total number of deliveries:

 0, n (%)

0 (0%)

0 (0%)

1,598 (10.5%)

595 (7.00%)

 1, n (%)

4,611 (6.71%)

2,894 (6.12%)

6,849 (45.1%)

4,041 (47.5%)

 2, n (%)

32,186 (46.8%)

23,368 (49.4%)

5,088 (33.5%)

3,056 (36.0%)

 3, n (%)

24,121 (35.1%)

16,357 (34.6%)

1,285 (8.46%)

654 (7.69%)

 4 or more, n (%)

7,784 (11.3%)

4,671 (9.88%)

378 (2.49%)

154 (1.81%)

Miscarriage, n (%)

20,866 (30.4%)

14,451 (30.6%)^b

1,950 (30.0%)^a

1,145 (29.6%)^a,b

Stillbirth, n (%)

872 (1.27%)

581 (1.23%)^b

198 (1.30%)

84 (0.99%)^b

Hypertensive disorders of pregnancy, n (%)

7,288 (10.6%)

5,186 (11.0%)^b

1,500 (9.87%)

870 (10.2%)^b

Preeclampsia + eclampsia, n (%)

5,143 (7.49%)

3,589 (7.59%)^b

1,080 (7.11%)

641 (7.54%)^b

Gestational diabetes, n (%)

1,495 (2.18%)

1,041 (2.20%)^b

127 (0.84%)

62 (0.73%)^b

Small for gestational age, n (%)

10,552 (15.8%)

7,354 (16.0%)^b

1,544 (10.2%)

862 (10.1%)^b

Large for gestational age, n (%)

14,620 (21.7%)

9,880 (21.3%)^b

1,733 (11.4%)

1,070 (12.6%)^b

Spontaneous preterm birth, n (%)

6,282 (9.18%)

4,187 (8.89%)^b

2,643 (17.5%)

1,509 (17.8%)^b