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Table 1 Potential confounding factors in relation to maternal smoking during pregnancy in controls

From: Prenatal smoking exposure and neuropsychiatric comorbidity of ADHD: a finnish nationwide population-based cohort study

  

No smoking

Smoking only in first trimester

Smoking after first trimester

p

χ 2

Maternal age at birth

≤19 years

529 (1.7 %)

48 (7.9 %)

322 (6.4 %)

p < 0.001

647.55

20–29 years

15,660 (50.1 %)

365 (59.8 %)

2836 (56.2 %)

30–39 years

14,195 (45.4 %)

186 (30.5 %)

1762 (34.9 %)

≥40 years

886 (2.8 %)

11 (1.8 %)

123 (2.4 %)

Paternal age at birtha

≤19 years

106 (0.3 %)

11 (1.9 %)

95 (1.9 %)

p < 0.001

413.72

20–29 years

11,414 (36.8 %)

297 (49.9 %)

2255 (45.9 %)

30–39 years

16,485 (53.1 %)

247 (41.5 %)

2160 (44.0 %)

≥40 years

3052 (9.8 %)

40 (6.7 %)

404 (8.2 %)

History of maternal psychopathology

Yes

3321 (10.6 %)

92 (15.1 %)

927 (18.4 %)

p < 0.001

258.83

No

27,949 (89.4 %)

518 (84.9 %)

4116 (81.6 %)

History of maternal substance abuse

Yes

357 (1.1 %)

22 (3.6 %)

368 (7.3 %)

p < 0.001

837.97

No

30,913 (98.9 %)

588 (96.4 %)

4675 (92.7 %)

History of paternal psychopathologya

Yes

3387 (10.9 %)

109 (18.3 %)

1101 (22.4 %)

p < 0.001

528.64

No

27,670 (89.1 %)

486 (81.7 %)

3813 (77.6 %)

Previous births

0

12,557 (40.2 %)

381 (62.5 %)

2139 (42.4 %)

p < 0.001

129.23

≥1

18,713 (59.8 %)

229 (37.5 %)

2904 (57.6 %)

Weight for gestational ageb

<-2 SD

716 (2.3 %)

16 (2.6 %)

285 (5.7 %)

p < 0.001

219.66

-2 to +2 SD

29,330 (94.1 %)

571 (93.9 %)

4641 (92.4 %)

≥ + 2 SD

1141 (3.7 %)

21 (3.5 %)

95 (1.9 %)

Maternal SES

Upper white collar

5325 (17.0 %)

40 (6.6 %)

263 (5.2 %)

p < 0.001

1179.59

Lower white collar

14,404 (46.1 %)

234 (38.4 %)

1890 (37.5 %)

Blue collar

4809 (15.4 %)

161 (26.4 %)

1552 (30.8 %)

Others

4663 (14.9 %)

129 (21.2 %)

901 (17.9 %)

Missing

2069 (6.6 %)

46 (7.5 %)

437 (8.7 %)

Maternal immigrant status

Not born in Finland

491 (1.6 %)

13 (2.1 %)

38 (0.8 %)

p < 0.001

21.91

Born in Finland

30,779 (98.4 %)

597 (97.9 %)

5005 (99.2 %

Paternal immigrant statusa

Not born in Finland

557 (1.8 %)

9 (1.5 %)

85 (1.7 %)

p < 0.841

0.35

Born in Finland

30,500 (98.2 %)

586 (98.5 %)

4829 (98.3 %)

Apgar score at 1 minc

<6

1151 (3.7 %)

30 (4.9 %)

195 (3.9 %)

p < 0.229

2.95

7–10

30,086 (96.3 %)

577 (95.1 %)

4841 (96.1 %)

Gestational age d

≤32 weeks

195 (0.6 %)

3 (0.5 %)

47 (1.0 %)

p < 0.029

14.11

33–36 weeks

1171 (3.8 %)

19 (3.1 %)

218 (4.3 %)

37–41 weeks

28,407 (91.0 %)

553 (90.8 %)

4546 (90.5 %)

≥42 weeks

1431 (4.6 %)

34 (5.6 %)

212 (4.2 %)

  1. adata missing: 357 subjects
  2. bdata missing: 145 subjects
  3. cdata missing 43 subjects
  4. ddata missing 87 subjects
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BMC Psychiatry

ISSN: 1471-244X

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