Paternal smoking and preterm birth: a population-based retrospective cohort study among non-smoking women aged 20–49 years in rural China

BACKGROUND: To comprehensively evaluate the association of paternal smoking and preterm birth (PTB). METHODS: We performed a population-based retrospective cohort study in rural areas of China among 5,298,043 reproductive-aged couples who participated in the National Free Pre-Pregnancy Checkups Project (NFPCP), regarding outcome events that occurred in 2010–2016. Multivariate Cox proportional regression was used to estimate hazard ratio (HR) and 95% confident intervals (95%CI), and restricted cubic spline (RCS) were used to estimate the dose–response relationship. RESULTS: Compared to neither-smoker couples, the fully adjusted HR for PTB was 1.04 (95% CI, 1.03–1.04), 1.08 (0.96–1.22), and 1.11 (1.03–1.19) in the couples where only the female smoked, only the male smoked and both, respectively. HR of PTB for paternal smoking was 1.07 (1.06–1.07), compared with women without paternal smoking. Consistent with paternal smoking, preconception paternal smoking showed 1.07-fold higher risk of PTB (95%CI, 1.06–1.09). The multivariable-adjusted HRs of PTB were 1.05 (1.03–1.06), 1.04 (1.03–1.05), 1.05 (1.04–1.07), 1.07 (1.05–1.10) and 1.13 (1.12–1.14) for participants whose husband smoked 1–4, 5–9, 10–14, 15–19, and ≥ 20 cigarettes/day respectively, compared with participants without paternal smoking. The HRs of PTB also increased with the increment of paternal smoking and preconception paternal smoking categories (P(linear) < 0.05). CONCLUSIONS: Paternal smoking and preconception paternal smoking was independently positively associated with PTB risk. The importance of tobacco control, should be emphasized during preconception and pregnancy counselling should be towards not only women but also their husband. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12978-022-01378-x.