Background: The role of paternal ageing on the incidence of some genetic diseases in offspring depends on the hypothesis that spontaneous mutations accumulate due to continuous cell divisions during spermatogenesis. We examined the effect of paternal age on the complex multifactorial character, stillbirth. Methods: In 3 619 647 Italian singletons born in 1990-1996 we evaluated stillbirth risk as a function of paternal ageing by means of multiple logistic regression models, which included maternal age and family education, as categorical covariates and interactions. The categorical risk was estimated for mothers and fathers beyond threshold ages of 35 and 40 years, respectively. Results: Stillbirth risk increases with paternal ageing in mothers greater than or equal to30 years old, and maternal age and family education modify the impact. In families with low education, the risk accounts for odds ratio (OR) 1.015 [95% confidence interval (CI) 1.01-1.02] in mothers aged 30-34 years, and for OR 1.032 (95% CI 1.02-1.04) in mothers aged greater than or equal to35 years; in families with higher education the risk accounts for OR 1.008 (95% CI 1.00-1.02) and OR 1.025 (95% CI 1.01-1.04), respectively, in mothers aged 30-34 and greater than or equal to35 years. In these latter families, for mothers aged <35 and fathers greater than or equal to40 years the risk accounts for OR 1.12 (95% CI 1.00-1.25). Conclusions: The effect of paternal ageing on stillbirth risk is revealed in mothers aged greater than or equal to30 years and is modified by family education. In mothers aged 30-34 years from families with high education, the increase imputable to paternal ageing might be indicative of a genetic component.
