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Table 2 Result summary: maternal smoking in pregnancy and the risk of stillbirth

From: Maternal smoking and the risk of still birth: systematic review and meta-analysis

Assessment criteria Odds ratio 95% CI
i) Overall pooled Results from main meta-analysis (25 studies) 1.47 1.37-1.57
ii) Subgroup analysis by daily amount of cigarettes consumption
1-9 cig/day (6 studies) 1.09 0.97-1.24
≥ 10 cig/day (7 studies) 1.52 1.30-1.78
iii) Subgroup analysis by gestation period at which stillbirth occurred
Stillbirth ≥ 20 weeks (11 studies) 1.43 1.32-1.54
Stillbirth ≥ 24 week (4 studies) 1.58 1.21-2.06
Stillbirth ≥ 28 weeks (7 studies) 1.33 1.18-1.49
iv) Subgroup analysis by geographic location
North America (9 studies) 1.39 1.29-1.50
Europe (11 studies) 1.55 1.36-1.78
Asia (1 study) 1.23 0.92-1.64
South America (1 study) 1.40 1.00-1.96
Australia (3 studies) 1.29 1.07-1.55
v) Subgroup analysis by quality
High score (14 studies) 1.41 1.28-1.55
Low score (11 studies) 1.49 1.33-1.67