Table 1 Background characteristics of the sample (n = 147,375)

Socioeconomic background

Age (years)

< 0.0001

< 0.0001

 < 25

213

24.2

2829

16.9

15,757

12.1

 25–34

520

59.1

10,319

61.5

85,585

66.0

 ≥ 35

147

16.7

3641

21.7

28,364

21.9

Marital status

< 0.0001

< 0.0001

 Married/cohabiting

621

71.6

14,251

87.4

115,804

94.4

 Single

91

10.5

751

4.6

2169

1.8

 Other

155

17.9

1302

8

4756

3.9

Level of education

< 0.0001

< 0.0001

 Not completed compulsory schooling^b (< 9 years)

255

37.4

2696

17.6

245

0.2

 Compulsory schooling (9 years)

101

14.8

1761

11.5

8317

6.4

 Upper secondary school (11–12 years)

143

21.0

4910

32.1

46,135

35.7

 Post-secondary education (vocational qualification & university)

183

26.8

5943

38.8

74,617

57.7

Mother’s income

< 0.0001

< 0.0001

 ≤ 25 percentile

754

89.5

10,369

63.2

25,687

19.8

 25–75 percentile

82

9.7

4922

29.4

68,547

52.9

 ≥ 75 percentile

6

0.7

1461

8.7

35,362

27.3

Migration

 Region of birth

< 0.0001

 Sub-Saharan Africa

392

44.6

3595

21.4

 North Africa & Middle East

396

45.1

8348

49.7

 Central Europe Eastern Europe & Central Asia

76

8.6

3283

19.6

 South and East Asia & Oceania

10

1.1

1241

7.4

 Other

5

0.6

322

1.9

Reason for immigration

< 0.0001

 Work/education

14

1.7

325

2.1

 Refugee

301

36.4

4817

30.9

 Family reunion

472

57.1

8215

52.7

 Other

39

4.7

2241

14.4

Length of Residence

< 0.0001

 < 2 years

347

41.2

2966

17.7

 2–5 years

319

37.9

3741

22.3

 6–9 years

139

16.5

3186

19.0

 ≥10 years

37

4.4

6885

41.0

Obstetric history

 Previous caesarean section

98

12.9

1872

11.7

0.287

11,221

8.7

< 0.0001

 Previous stillbirth

21

2.4

260

1.5

0.053

805

0.6

< 0.0001

Present pregnancy

 Parity

< 0.05

< 0.05

 Nulliparous

379

43.1

6440

38.4

61,459

47.4

 Parous

500

56.9

10,349

61.6

68,247

52.6

 Smoking in early pregnancy

19

2.2

906

5.6

< 0.0001

7583

6.2

< 0.0001

 Chronic hypertension

0

0

41

0.2

0.142

516

0.4

0.061

 Diabetes Mellitus type 1 or 2

3

0.3

72

0.4

0.696

884

0.7

0.220

 Gestational diabetes

12

1.4

414

2.5

< 0.05

1104

0.9

0.100

 Pre-eclampsia/eclampsia

18

2.0

418

2.5

0.408

4059

3.1

0.065

Pre-pregnancy BMI (kg/m²)

< 0.0001

< 0.0001

 Underweight (< 18.5)

24

2.9

425

2.8

2354

2

 Normal weight (18.5–24.9)

353

42.6

7904

51.5

73,085

62.6

 Overweight (25.0-29.9)

268

32.3

4676

30.5

27,953

24

 Obesity (≥ 30)

184

22.2

2334

15.2

13,317

11.4

Antenatal care visits (No)

< 0.001

< 0.0001

 < 8

115

13.2

2963

18.1

21,997

17.0

 8–12

544

62.7

10,132

62

82,289

66.6

 > 12

209

24.1

3258

19.9

19,334

15.6

Gestational weeks (gwks)

< 0.0001

< 0.0001

 Preterm < 37

19

2.2

942

5.6

7278

5.6

 Term 37–41

714

81.1

14,433

86.0

112,678

86.9

 Post-term ≥ 42

147

16.7

1410

8.4

9740

7.5

Birth weight, (grams)

< 0.05

0.013

 ≤ 2500

26

3.0

888

5.3

4865

3.8

 2501–4500

834

94.8

15,566

92.8

119,528

92.2

 > 4500

20

2.3

319

1.9

5210

4.0