Table 4 Comparison of the characteristics of the Hokkaido cohort participants included and lost to follow-up

 Age at entry (years)

19,549

29.9

29.8–29.9

1166

29.4

29.1–29.7

4831

29.9

29.8–30.0

 Maternal body mass index

18,428

21.2

21.1–21.2

1141

20.9

20.7–21.0

4608

21.2

21.1–21.3

 Nulliparous (%)

7226

42.1

41.4–42.9

595

54.5

51.5–57.4

1726

40.9

39.4–42.3

 History of reproductive therapy (%)

925

4.9

4.6–5.3

73

6.2

5.0–7.8

259

5.5

4.9–6.2

 Regular use of any medicine (%)

1956

10.3

9.8–10.7

139

11.3

9.7–13.2

519

11.0

10.1–11.9

 Regular use of any supplement (%)

5852

30.7

30.0–31.3

378

30.8

28.3–33.5

1565

33.1

31.8–34.5

 Drinking habit at 1st trimester (%)

2180

11.7

11.3–12.2

141

12.1

10.4–14.1

531

11.4

10.5–12.4

 Smoking habit 1st trimester (%)

2136

12.0

11.6–12.5

135

12.2

10.5–14.3

487

11.6

10.7–12.6

 Passive smoking in house (%)

11,752

65.9

65.2–66.6

687

61.2

58.3–64.0

2852

63.6

62.2–65.0

 Education, compulsory education only (%)

1011

5.4

5.1–5.7

74

6.4

5.1–7.9

247

5.3

4.7–6.0

 Occupation, no job

8137

41.6

40.9–42.3

499

40.7

38.0–43.5

2012

41.5

40.1–42.9

 Income, <3,000,000 yen/year (%)

3662

22.8

22.2–23.5

240

23.8

21.2–26.5

916

22.7

21.4–24.0

 Age at entry (years)

18,311

31.7

31.6–31.8

1135

31.1

30.8–31.4

4595

31.7

31.5–31.9

 Drinking habit (%)

13,375

72.1

71.5–72.8

863

75.2

72.6–77.6

3319

71.5

70.2–72.8

 Smoking habit 1st trimester (%)

10,855

66.4

65.7–67.1

650

64.3

61.3–67.2

2644

65.0

63.5–66.4

 Education, compulsory education only (%)

1431

7.8

7.4–8.2

78

6.9

5.6–8.5

347

7.5

6.8–8.3

 Occupation, no job

417

2.2

2.0–2.4

41

3.4

2.6–4.7

117

2.5

2.0–3.0