In this paper, we attempt to analyze the determinants of unintended births among Colombian women aged 40 years old or more using data from the Encuesta Nacional de Demografía y Salud 2005, which is Colombia’s national demographic and health survey. Given the especial characteristics of the variable under analysis, we used count data models in order to test whether certain characteristics of women and their socioeconomic backgrounds such as their level and years of schooling or socioeconomic group, explain the number of unintended births. We found that women’s education and the area of residence are significant determinants of unintended births. The inverse relationship between the level of education of women and the number of unintended births has key implications to social policies.