Background: It is well known that miscarriage risk increases with age. However, studies usually investigate only maternal age effects. We investigated both maternal age and paternal age effects on miscarriage risk to provide insight into this frequent reproductive failure.
Methods: The last planned pregnancies (n = 3174) that ended in a birth or miscarriage were analysed in a retrospective population-based study on women aged 25-44 years in Denmark, Germany, Italy and Spain. Maternal and paternal ages were analysed together, using a single variable 'couple age' in a multivariate logistic regression analysis, with couples composed of a woman and a man both aged 20-29 years forming the reference group.
Results: After adjustment for various factors (e.g. reproductive history, country), we found that the risk of miscarriage was higher if the woman was aged > or = 35 years, as has already been reported in a number of studies. However, the increase in risk was much greater for couples composed of a woman aged > or = 35 years and of a man aged > or = 40 years. Potential source of bias (especially 'reproductive compensation') are discussed.
Conclusions: The risk of an adverse pregnancy outcome is highest if both partners are advanced in age.