Paternal smoking cessation before pregnancy reduces the risk of spontaneous abortion: a population-based retrospective cohort study

BACKGROUND: During preconception counselling, pregnant women who smoke are advised to quit smoking. While the adverse effects of paternal smoking on pregnancy and perinatal outcomes have been increasingly recognised, the health benefits of paternal smoking cessation prior to conception remain understudied. METHODS: The current study involved non-smoking reproductive-aged Chinese women who participated two times in the National Free Prepregnancy Checkups Project during 2010-2018. A total of 158 986 pregnancies were included, with husbands reporting smoking at the preconception examination stage during their first participation. The primary exposure was paternal smoking cessation before pregnancy. And the primary outcome was spontaneous abortion (SAB) recorded in the second participation. Inverse-probability-weighted (IPW) logistic regression was used to estimate ORs and their 95% CIs of SAB with paternal smoking cessation before pregnancy. Instrumental variable (IV) analyses were further used to estimate the association. RESULTS: Compared with continued paternal smoking, paternal smoking cessation before pregnancy was associated with a reduced risk of SAB (IPW-adjusted OR 0.86 (95% CI 0.81 to 0.91); IV-estimated OR 0.79 (95% CI 0.76 to 0.82)). Additionally, a decrease in paternal smoking was also associated with a lower risk of SAB. Notably, the risk of SAB was still higher than that of those without paternal smoking in IV analysis (OR 1.21 (95% CI 1.26 to 1.32)). CONCLUSIONS: Paternal smoking cessation prior to conception is linked to a reduced risk of SAB. However, the risk of SAB among women with paternal smoking cessation was still higher than that among those without paternal smoking. Preconception counselling should advise fathers who smoke to quit.