Table 1 Baseline characteristics of participants in the control- and intervention-phase

Age (years)^a

31.0 (28.0–33.0)

31.0 (28.0–34.0)

33.0 (30.0–36.0)

33.0 (30.0–35.0)

  < 25

43 (5.3)

21 (10.1)

8 (5.2)

2 (5.1)

 25—29

266 (32.9)

58 (28.0)

20 (13.0)

5 (12.8)

 30—34

367 (45.4)

87 (42.0)

73 (47.4)

20 (51.3)

 35—39

117 (14.5)

32 (15.5)

40 (26.0)

6 (15.4)

  ≥ 40

16 (2.0)

9 (4.4)

13 (8.4)

6 (15.4)

 Missing data

41

6

Ethnical background

 Dutch

768 (94.9)

192 (92.8)

152 (98.8)

39 (100.0)

 Non-Dutch

41 (5.1)

15 (7.2)

2 (1.2)

0 (0.0)

 Missing data

41

6

Educational Level

 Low/Moderate

288 (35.7)

68 (32.9)

47 (30.7)

17 (43.6)

 High

519 (64.3)

139 (67.2)

106 (69.3)

22 (56.4)

 Missing data

43

6

1

Pre-pregnancy BMI^a

23.5 (21.5–27.1)

23.7 (21.6–26.4)

  < 18.5

13 (1.6)

3 (1.4)

 18.5 – 24.9

499 (62.1)

124 (60.0)

 25.0 – 29.9

177 (22.0)

46 (22.2)

  ≥ 30.0

115 (14.3)

34 (16.4)

 Missing data

46

6

Chronic illness

 Yes

110 (13.6)

32 (15.2)

 No

698 (86.4)

178 (84.8)

 Missing data

42

3

First time parent

 Yes

369 (45.6)

121 (58.5)

79 (51.3)

27 (69.2)

 No

440 (54.4)

86 (41.5)

75 (48.7)

12 (30.8)

 Missing data

41

6

Spontaneous conception

 Yes

762 (93.2)

188 (93.1)

143 (93.5)

38 (97.4)

 No

56 (6.8)

14 (6.9)

10 (6.5)

1 (2.6)

 Missing data

32

11

1