This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s10680-015-9371-z ; The role of religion in explaining fertility differences is often overlooked in demographic studies, particularly in Western Europe, where there has been a substantial decline in institutional forms of religious adherence. The current study explores the changing relationships between religion and childbearing in Britain, France and the Netherlands. Using data from the Generations and Gender Programme and the British Household Panel Survey, religious differences in completed fertility and the transition to first birth are explored across cohorts of women. In addition, a longitudinal analysis is employed to examine the influence of religion on subsequent childbearing. Although the secularization paradigm assumes that the influence of religion on individual behavior will diminish over time, it is found that religious affiliation and practice continue to be important determinants of fertility and family formation patterns. However, there is some variation in the relationship between religion and fertility across countries; while in France and the Netherlands fertility gaps by religiosity are either consistent or increasing, in Britain, this gap appears to have narrowed over time. These findings suggest that fertility differences by religion also depend on the particular social context of religious institutions in each country. ; This work was supported by the Clarendon Fund and Nuffield College, University of Oxford and by the Philomathia Social Sciences Research Programme, University of Cambridge.