Paternal smoking is associated with an increased risk of pregnancy loss in a dose-dependent manner: a systematic review and meta-analysis

Objective: To study the association between paternal lifestyle factors in the preconception period and the risk of pregnancy loss. Evidence Review: The Preferred Reporting Items for Systematic Reviews and Meta -analysis guidelines for systematic reviews and meta -analysis were followed. PubMed and Embase databases were searched up to August 2020. Original articles in English language addressing the relation between paternal exposure status in the preconception period and pregnancy loss were included. The paternal lifestyle factors examined were smoking, alcohol consumption, and body mass index. Studies that only examined exposure status during pregnancy (and not in the preconception period) and those that solely focused on pregnancy outcome after artificial reproductive technology were excluded. The qualitative risk of bias assessments was performed. Meta -analysis using a random -effects model was performed if sufficient data were available, with the risk of pregnancy loss as the primary outcome. Results: The systematic search included 3,386 articles, of which 11 met the inclusion criteria. In a meta -analysis of 8 studies, paternal smoking of >10 cigarettes per day in the preconception period was found to be associated with an increased risk of pregnancy loss, after adjustment for maternal smoking status (1-10 cigarettes per day, 1.01; 95% confidence interval [CI], 0.97-1.06; 11-19 cigarettes per day, 1.12; 95% CI, 1.08-1.16; >= 20 cigarettes per day, 1.23; 95% CI, 1.17-1.29). No clear association was found between paternal alcohol consumption and pregnancy loss, based on 5 available studies. No studies were identified evaluating the association between paternal body mass index and spontaneous pregnancy loss. Conclusion: Awareness of the association between paternal smoking in the preconception period and the risk of pregnancy loss should be raised. More well -designed studies are needed to further investigate the effects of other paternal lifestyle factors on the risk of pregnancy loss.