Association between preconception paternal smoking and birth defects in offspring: evidence from the database of the National Free Preconception Health Examination Project in China

Objective To clarify whether preconception paternal smoking has any adverse effects on the offspring. Design Prospective, population-based study. Setting Preconception registry data from the National Free Preconception Health Examination Project. Population or sample Couples planning pregnancy, with complete information on preconception paternal smoking behaviour and pregnancy outcomes. Methods The effect of questionnaire-based paternal smoking behaviour during preconception and pregnancy was assessed via logistic regression. Additionally, we performed a 1:1 case-control (birth defects versus normal pregnancy) analysis, matched for maternal province, folic acid supplementation and paternal alcohol consumption. Main outcome measures Risk of birth defects in offspring. Results In total, 566 439 couples with complete information on preconception paternal smoking behaviour and pregnancy outcomes were enrolled. The preconception paternal smoking rate was 28.7% (162 482) overall: 8.7% (49 303) stopped smoking, 13.3% (75 517) decreased their smoking, and 6.6% (37 662) continued smoking during early pregnancy. The risk of birth defects was higher in the continued-smoking (P < .000, odds ratio [OR] 1.87, 95% CI 1.36-2.56) and decreased-smoking groups (P = .007, OR 1.41, 95% CI 1.10-1.82). In the case-control analysis, infants whose fathers stopped (P = .003, OR 0.32, 95% CI 0.15-0.67) or decreased smoking (P = .000, OR 0.25, 95% CI 0.13-0.49) were at lower risk of congenital heart diseases, limb abnormalities, digestive tract anomalies and neural tube defects than those whose fathers continued smoking. Conclusion Preconception paternal smoking may be associated with congenital heart diseases, limb abnormalities and neural tube defects in the offspring. Changes in smoking behaviour may reduce this risk. Tweetable abstract This study suggests that preconception paternal smoking is associated with birth defects in offspring. Changes in smoking behaviour may reduce this risk.