Table 3 Main and stratified analysis of association between pregnancy exposure to NO₂ and birth weight

 Entire study population

17523

−37.9 (−49.7 to −26.0)

<0.001

16273

−43.6 (−55.8 to −31.5)

<0.001

16273

−5.6 (−23.6 to 12.4)

0.54

15829

−7.4 (−19.6 to 4.8)

0.24

 Women who did not change address

15191

−37.4 (−50.2 to −24.7)

<0.001

14196

−42.7 (−55.7 to −29.6)

<0.001

14196

−7.0 (−26.3 to 12.3)

0.48

13818

−4.7 (−17.8 to 8.4)

0.48

 LMP-based GA only

16805

−35.4 (−47.5 to −23.2)

<0.001

15618

−40.8 (−53.3 to −28.4)

<0.001

15618

−3.2 (−21.6 to 15.1)

0.73

15195

−5.8 (−18.3 to 6.7)

0.36

 Oslo

4669

7.5 (−27.7 to 42.7)

0.68

4380

−5.9 (−42.8 to 31.0)

0.75

4285

12.5 (−24.3 to 49.3)

0.51

 Akershus

7547

10.5 (−22.8 to 43.9)

0.54

6982

8.9 (−25.4 to 43.1)

0.61

6759

29.2 (−4.8 to 63.1)

0.09

 Bergen

3866

−15.6 (−43.7 to 12.4)

0.28

3577

−4.8 (−33.0 to 23.4)

0.74

3490

19.8 (−7.7 to 47.2)

0.16

 Hordaland

1441

−37.6 (−104.6 to 29.4)

0.27

1334

−36.0 (−103.5 to 31.5)

0.30

1295

−26.7 (−92.7 to 39.2)

0.43

 Not smoking

15440

−41.3 (−53.8 to −28.8)

<0.001

15229

−43.3 (−55.8 to −30.8)

<0.001

15229

−6.6 (−25.1 to 12.0)

0.49

14835

−5.6 (−18.2 to 6.9)

0.38

 Smoking

1083

−28.3 (−80.0 to 23.3)

0.28

1044

−45.5 (−97.7 to 6.8)

0.09

1044

22.1 (−51.8 to 96.1)

0.56

994

−27.3 (−80.1 to 25.5)

0.31

 Parity 0

8304

−16.8 (−33.3 to −0.4)

0.045

7803

−17.8 (−34.7 to −1.0)

0.04

7803

4.3 (−20.5 to 29.0)

0.74

7594

−8.3 (−25.2 to 8.5)

0.33

 Parity 1

6326

−0.6 (−20.6 to 19.4)

0.95

5858

−6.9 (−27.4 to 13.5)

0.51

5858

21.8 (−8.2 to 51.8)

0.15

5695

2.0 (−18.3 to 22.4)

0.85

 Parity ≥2

2893

−26.5 (−60.3 to 7.4)

0.13

2612

−31.0 (−66.4 to 4.4)

0.09

2612

17.8 (−31.7 to 67.4)

0.48

2540

−24.8 (−59.9 to 10.4)

0.17

 Boys

8921

−30.7 (−47.5 to −13.8)

<0.001

8290

−39.6 (−57.0 to −22.2)

<0.001

8290

−7.5 (−33.0 to 18.1)

0.57

8040

−5.4 (−22.8 to 12.1)

0.55

 Girls

8602

−45.5 (−62.0 to −29.1)

<0.001

7983

−47.8 (−64.8 to −30.8)

<0.001

7983

−3.6 (−28.9 to 21.8)

0.78

7789

−9.4 (−26.4 to 7.6)

0.28

 Education less than high school

985

−35.4 (−95.3 to 24.5)

0.25

968

−24.5 (−83.4 to 34.5)

0.42

968

−18.4 (−96.7 to 60.0)

0.65

905

−27.8 (−87.2 to 31.5)

0.36

 Education high school

4173

−31.9 (−58.5 to −5.3)

0.02

4098

−36.0 (−62.3 to −9.7)

0.007

4098

10.4 (−27.3 to 48.1)

0.59

3948

4.8 (−21.7 to 31.3)

0.72

 Education up to 4 years of college

6474

−42.4 (−61.5 to −23.3)

<0.001

6403

−44.0 (−62.8 to −25.3)

<0.001

6403

−1.5 (−30.2 to 27.1)

0.92

6262

−4.9 (−23.7 to 13.9)

0.61

 Education more than  4 years of college (master or professional degree)

4866

−48.2 (−69.6 to −26.9)

<0.001

4804

−50.2 (−71.4 to −29.0)

<0.001

4804

−17.8 (−49.4 to 13.8)

0.27

4714

−13.3 (−34.5 to 8.0)

0.22

 Born in winter

4097

−20.2 (−46.6 to 6.2)

0.13

3797

−35.3 (−62.5 to −8.2)

0.01

3797

7.8 (−31.1 to 46.7)

0.69

3677

4.9 (−22.4 to 32.1)

0.73

 Born in spring

4684

−60.6 (−82.2 to −39.0)

<0.001

4355

−60.2 (−82.2 to −38.3)

<0.001

4355

−46.7 (−79.5 to −13.8)

0.005

4226

−28.5 (−50.6 to −6.4)

0.01

 Born in summer

4626

−35.1 (−57.4 to −12.8)

0.002

4272

−40.5 (−63.3 to −17.6)

0.001

4272

14.2 (−20.7 to 49.1)

0.43

4167

−2.7 (−25.7 to 20.3)

0.82

 Born in autumn

4116

−28.8 (−54.9 to −2.7)

0.03

3849

−31.9 (−58.6 to −5.3)

0.02

3849

16.1 (−23.0 to 55.1)

0.42

3759

5.1 (−21.4 to 31.7)

0.70