Table 1 Characteristics of the mothers and children and their associations with childhood asthma in the case - control study

< 0.0001

  ≤ 9

37 (5.8)

161 (18.6)

0.2

0.2–0.4

 10–12

85 (13.4)

147 (17.0)

0.6

0.5–0.8

 13–16

406 (64.0)

434 (40.2)

ref

ref

  ≥ 17

51 (8.0)

42 (4.7)

1.3

0.8–2.0

 Unknown

55 (8.7)

80 (9.3)

0.7

0.5–1.1

0.002

 No

589 (92.9)

834 (96.5)

ref

ref

 Yes

45 (7.1)

30 (3.5)

2.1

1.3–3.4

Maternal age at delivery (years)

28.5 (3.6)

27.7 (3.8)

0.0004

1.1

1.0–1.1

Gestational weeks at birth

38.8 (1.4)

38.9 (1.4)

0.1

0.9

0.9–1.0

Birth weight (g)

3305.6 (480.9)

3283.9 (500.4)

0.1

1.0

1.0–1.0

Delivery modes

0.02

 Vaginal delivery

237 (37.4)

376 (43.5)

ref

ref

 Caesarean delivery

397 (62.6)

488 (56.5)

1.3

1.0–1.6

0.5

 No

303 (47.8)

399 (46.2)

ref

ref

 Yes

331 (52.2)

465 (53.8)

0.9

0.8–1.2

Child age (years)

5.7 (2.0)

6.3 (2.2)

< 0.0001

0.8

0.8–0.9

Child gender

0.002

 Female

252 (39.8)

414 (47.9)

ref

ref

 Male

382 (60.2)

450 (52.1)

1.4

1.1–1.7

0.7

 Han

612 (96.5)

837 (96.8)

ref

ref

 Other

16 (2.5)

22 (2.6)

1.0

0.5–1.9

 Unknown

6 (1.0)

5 (0.6)

1.6

0.5–5.4

< 0.0001

 No

289 (45.6)

679 (78.6)

ref

ref

 Yes

334 (52.7)

173 (20.0)

4.5

3.6–5.7

 Unknown

14 (1.7)

12 (1.4)

2.2

0.9–4.9