| | Study | Exposure to parental smoking | Number of case/control | OR (95% CI) | Adjustments | | Paternal smoking | Maternal smoking |
| | Lee et al. 2009, Korea [42]* |
Ever smoked cigarettes | Adjusted for age, sex, birth weight, father's education | | Lifetime nonsmokers | Lifetime nonsmokers | 22/41 | reference | | ever | lifetime nonsmokers | 84/122 | 1.3 (0.7, 2.4) | |
pack-years before pregnancy | | 0 | lifetime nonsmokers | 22/41 | reference | | ≤10 | lifetime nonsmokers | 48/60 | 1.6 (0.8, 3.1) | | >10 | lifetime nonsmokers | 28/33 | 1.6 (0.8, 3.5) | | Smoking at home during pregnancy | | | | | Lifetime nonsmokers | lifetime nonsmokers | 22/41 | reference | | yes | lifetime nonsmokers | 22/22 | 2.1 (0.9, 4.9) | | | | | |
pack-years after birth | | 0 | lifetime nonsmokers | 27/55 | reference | | ≤10 | lifetime nonsmokers | 64/77 | 1.7 (0.9, 3.1) | | >10 | lifetime nonsmokers | 11/11 | 3.0 (1.0, 8.8) |
| | Ji et al. 1997, China [41] |
pack-years before pregnancy | Adjusted for birth weight, income, paternal age, education, and alcohol drinking | | 0 | lifetime nonsmokers | — | reference | | ≤2 | lifetime nonsmokers | — | 0.8 (0.2–2.5) | | 2 to 5 | lifetime nonsmokers | — | 1.0 (0.4–2.7) | | ≥5 | Lifetime nonsmokers | — | 3.8 (1.3–12.3) | | Pack-years after pregnancy | | | | | 0 | lifetime nonsmokers | — | reference | | ≤2 | lifetime nonsmokers | — | 1.1 (0.4, 2.8) | | 2 to 5 | lifetime nonsmokers | — | 1.8 (0.6, 5.2) | | ≥5 | lifetime nonsmokers | — | 1.8 (0.6, 5.5) |
| | Chang et al. 2006, USA [23] | No preconception smoking | no postnatal smoking | 144/205 | reference | household income and maternal smoking during preconception and pregnancy | | No preconception smoking | postnatal smoking | 8/27 | 0.72 (0.22, 2.38) | | Preconception smoking | no postnatal smoking | 36/47 | 0.88 (0.51, 1.52) | | Preconception smoking | postnatal smoking | 37/23 | 3.94 (1.25, 12.37) |
| | Brondum et al. 1999, USA [21] | Never smoked in the home | never smoking in the home | — | reference | Adjusted for household income, mother's and father's race and education | | Never smoked in the home | ever smoked in the home | — | 1.10 (0.88, 1.38) | | Ever smoked in the home | never smoking in the home | — | 1.04 (0.86, 1.26) | | Ever smoked in the home | ever smoked in the home | — | 1.09 (0.91, 1.30) |
| | John et al. 1991, USA [27] | Not during the year prior to birth | not during the 1st trimester | — | reference | Adjusted for father's education | | Not during the year prior to birth | yes, during the 1st trimester | — | 1.9 (0.9, 4.1) | | Yes, during the year prior to birth | not during the 1st trimester | — | 1.4 (0.6, 3.1) | | Yes, during the year prior to birth | yes, during the 1st trimester | — | 1.8 (0.8, 4.0) |
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