ORIGINAL ARTICLE Reproductive epidemiology Too old to have children? Lessons from natural fertility populations

study question: Is it possible to construct an age curve denoting the ages above which women are biologically too old to reproduce? summaryanswer:Weconstructed a curvebasedon the distribution of female age at last birth in natural fertility populations reflecting the ages above which women have become biologically too old to have children. what is known already: The median age at last birth (ALB) for females is 40–41 years of age across a range of natural fertility populations. This suggests that there is a fairly universal pattern of age-related fertility decline. However, little is known about the distribution of female ALB and in the present era of modern birth control, it is impossible to assess the age-specific distribution of ALB. Reliable information is lacking that could benefit couples who envisage delaying childbearing. study design, size, duration: This study is a review of high-quality historical data sets of natural fertility populations in which the distributions of female age at last birth were analysed. The studies selected used a retrospective cohort design where women were followed as they age through their reproductive years. participants/materials, setting, methods: Using a common set of eligibility criteria, large datafiles of natural fertility popu