In 2006, the teen birth rate rose for the first time since 1991. Between 2005 and 2006, the birth rate increased 3 percent for teens aged 15-17 and 4 percent for teens aged 18-19. Teenage childbearing has negative consequences both for the mothers involved and for their children. For example, teen mothers and their children experience poorer educational, health, economic, and developmental outcomes than do women who delay childbearing beyond their teen years and their children. Moreover, this is the case even after accounting for the fact that teen mothers tend to be from disadvantaged backgrounds prior to giving birth. Given such evidence, policymakers, program providers, and the general public share a keen interest in preventing early motherhood. This "Research Brief" provides new state-level information on teen childbearing. To produce the brief, Child Trends analyzed the most recent data on births by state (2006) to estimate the percentage of females who will become mothers before age 20. Statistics on teen childbearing usually are presented in terms of birth rates (the number of births per 1,000 females). Calculating the percentage of females who are estimated to become teen mothers provides additional information that will allow policymakers and program providers to better understand how many young women in their respective states are at risk of early childbearing. Across the country, the estimated proportion of females who will become teen mothers decreased from 25 percent in 1991 to 18 percent in 2006. However, our analyses show that states vary widely in the estimated percentage of females who will have a baby during their teen years, ranging from less than 10 percent in states with the lowest teen birth rates to 30 percent in the state with the highest teen birth rate. (Contains 1 figure and 2 tables.)