Table 2 Multiple-imputation analysis of the relationship between body-mass index, smoking and alcohol intake with risk of miscarriage excluding induced abortions (n = 23,503)

Body-mass index

Underweight

1204

278 (23.1)

1.08 (0.96, 1.22), 0.2

1.07 (0.94, 1.21), 0.3

1.07 (0.94, 1.21), 0.3

Normal weight

13,505

2918 (21.6)

Ref

Ref

Ref

Overweight

5506

1253 (22.8)

1.05 (0.98, 1.12), 0.1

1.02 (0.96, 1.09), 0.5

1.03 (0.96, 1.09), 0.4

Obese

3288

868 (26.4)

1.22 (1.14, 1.32), < 0.001

1.13 (1.05, 1.21), 0.001

1.14 (1.06, 1.23), < 0.001

Smoking

Never smoker

13,071

2749 (21.0)

Ref

Ref

Ref

Former smoker

5712

1326 (23.2)

1.10 (1.03, 1.17), 0.003

0.99 (0.94, 1.06), 0.9

0.98 (0.92, 1.04), 0.5

< 10 cigarettes per day

1814

442 (24.4)

1.16 (1.05, 1.28), 0.003

1.02 (0.93, 1.13), 0.6

1.00 (0.91, 1.10), 0.9

10–19 cigarettes per day

1404

397 (28.3)

1.37 (1.24, 1.51), < 0.001

1.13 (1.02, 1.25), 0.02

1.09 (0.98, 1.21), 0.1

20 or more cigarettes per day

889

244 (27.4)

1.34 (1.19, 1.51), < 0.001

1.07 (0.94, 1.21), 0.3

1.03 (0.91, 1.17), 0.6

Unknown amount of smoking

613

159 (25.9)

1.30 (1.13, 1.50), < 0.001

1.06 (0.90, 1.25), 0.5

1.02 (0.86, 1.22), 0.8

Alcohol intake

Low risk drinker

19,957

4544 (22.8)

Ref

Ref

Ref

Non-drinker

2700

513 (19.0)

0.81 (0.74, 0.89), < 0.001

0.82 (0.75, 0.89), < 0.001

0.81 (0.74, 0.89), < 0.001

Risky drinker

846

260 (30.7)

1.36 (1.22, 1.52), < 0.001

1.15 (1.03, 1.28), 0.02

1.13 (1.01, 1.27), 0.04