Described as ‘one of the most remarkable changes in social behaviour in the twentieth century1, declining fertility is related to wider changes in families and relationships occurring in recent decades such as later marriage, increased cohabitation, and increased divorce and cohabitation breakdown. Declining fertility combined with low rates of mortality results in population ageing and potentially population decline2. These have implications for areas such as social security provision and labour supply, as well as the provision of unpaid care. It has been suggested that one important factor explaining declining fertility is higher levels of delayed childbearing and increased childlessness. This research investigates some of the factors associated with later childbearing and childlessness amongst men and women in Britain and whether these have changed over time. Through analysing data from large-scale cohort studies, the 1958 National Child Development Study (NCDS) and the 1970 British Cohort Study (BCS), this ESRC funded project compared fertility patterns of those born in 1958 and 1970.