Table 1 Basic characteristics of the participants and the non-participants having live birth in the adjunct study of JECS

Mothers with live birth

8873

1823

7050

Age at delivery (yrs)

8823

30.7 ± 5.1

1817

31.0 ± 5.3

7006

30.6 ± 5.0

0.0022

Marital status at registration (Married, %)

8798

94.7

1807

94.3

6991

94.8

0.39

Maternal education (<13 yrs, %)

8746

52.9

1790

54.1

6956

52.3

0.27

Paternal education (<13 yrs, %)

8695

59.3

1778

62.9

6917

59.6

0.013

  < 2

575

7.4

121

7.4

454

7.4

0.15

 2 to <4

3111

39.9

694

42.6

2417

39.2

 4 to <6

2290

29.4

454

27.8

1836

29.8

 6 to <8

972

12.5

205

12.6

767

12.5

  ≥ 8

842

10.8

157

9.6

685

11.1

Living together with parents (Yes, %)

8835

46.7

1818

43.3

7017

47.5

0.0012

 Never smoked

4324

49.0

842

46.4

3482

49.6

0.034

 Ex-smokers who quit before pregnancy

2099

23.8

440

24.2

1659

23.6

 Ex-smokers who quit after pregnancy

1752

19.8

377

20.8

1375

19.6

 Smokers during early pregnancy

657

7.4

157

8.6

500

7.1

Passive smoking (Yes, %)

8850

66.4

1819

69.2

7031

65.7

0.0047

Alcohol consumption (Drinkers, %)

8767

2.5

1791

1.7

6976

2.7

0.013

Prepregnancy BMI (kg/m2)

8872

21.8 ± 3.6

1823

21.9 ± 3.9

7049

21.7 ± 3.6

0.019

Body weight gain at delivery (kg)

8822

10.8 ± 4.2

1813

10.4 ± 4.2

7009

10.9 ± 4.1

<0.0001

Physical activity (mets · min/week)

8766

480 (0–18400)

1792

480 (0–18400)

6974

480 (0–16400)

0.81

 Diabetes mellitus

8866

0.73

1822

0.49

7044

0.80

0.16

 Gestational diabetes mellitus

8866

1.5

1822

1.1

7044

1.6

0.11

 Pregnancy-induce hypertension

8866

1.1

1822

2.4

7044

0.82

<0.0001

 Hyperthyroidism

8866

0.43

1822

0.27

7044

0.47

0.23

 Intrauterine growth restriction

8866

1.2

1822

1.4

7044

1.2

0.37

 Placenta abruption

8866

0.20

1822

0.0

7044

0.26

0.035^a

Parity (Primipara, %)

8783

39.4

1789

37.8

6994

39.8

0.12

Infertility treatment (Yes, %)

8814

4.6

1812

5.9

7002

4.3

0.0059

Fish intake (g/day)

8757

29.1 (0.8–919)

1788

1788 28.3 (1.2–612)

6969

29.4 (0.8–919)

0.11

Meat intake (g/day)

8762

54.6 (0.4–1740)

1789

55.5 (0.4–1581)

6973

54.3 (1.5–1740)

0.21

 Any kind

8774

38.8

1793

34.2

6981

40.0

<0.0001

 EPA and/or DHA

8773

2.2

1792

2.5

5981

2.1

0.30

Breakfast skipper (Skipper, %)

8756

13.8

1788

14.8

6968

13.5

0.14

Housewife (Yes, %)

8742

44.0

1787

50.6

6955

42.3

<0.0001

 Singleton births (%)

8873

99.2

1823

99.2

7050

99.1

0.69

Gestational age at birth (day)

8857

274.1 ± 11.8

1819

273.6 ± 13.5

7038

274.3 ± 11.3

0.025

 Preterm births (<37) (%)

8857

5.5

1819

5.4

7038

5.5

0.93

Sex (Male, %)

8865

51.0

1822

51.6

7043

50.9

0.35

Type of delivery (Transvaginal, %)

8847

82.2

1819

81.9

7028

82.2

0.74

 All

8850

3046 ± 441

1818

3031 ± 479

7032

3050 ± 431

0.12

 Male

4481

3095 ± 433

939

3076 ± 485

3580

3089 ± 433

0.43

 Female

4289

3010 ± 427

876

2984 ± 468

3450

3008 ± 424

0.15

 Low birth weight (<2500 g) (%)

8850

8.2

1818

9.8

7032

7.8

0.005