Table 2. Association between periconceptional passive smoking and risk for fetal NTDs in five counties, Shanxi Province, China, 2010–2016.
| Passive smoking exposure | Case | Control | Crude OR (95% CI) | Adjusted OR* (95% CI) |
| * Adjusted for maternal age, pregnancy BMI, education, fever or flu in early pregnancy, nausea and vomiting during pregnancy (NVP), periconception folic acid use and history of birth defect-affected pregnancy; Ptrend<0.001.
Abbreviations: NTDs=neural tube defects; OR=odds ratio; CI=confidence interval; BMI=body mass index. | ||||
| No | 91 | 369 | 1.0 | 1.0 |
| Yes (any exposure) | 133 | 154 | 3.502 (2.527–4.853) | 3.227 (2.213–4.704) |
| 1–3 times/week | 37 | 75 | 2.000 (1.268–3.155) | 1.878 (1.115–3.163) |
| 4–6 times/week | 24 | 37 | 2.630 (1.499–4.617) | 2.584 (1.348–4.954) |
| >6 times/week | 72 | 42 | 6.951 (4.458–10.840) | 6.114 (3.673–10.178) |