BACKGROUND: A substantial number of young women experience pregnancy scares – thinking they might be pregnant, and later discovering that they are not. Although pregnancy scares are distressing events, little is known about who experiences them and whether they are important to our understanding of unintended pregnancy. OBJECTIVE: We describe the young women who experience pregnancy scares, and examine the link between pregnancy scares and subsequent unintended pregnancy. METHODS: We used data from the Relationship Dynamics and Social Life Study. T-tests and regression analyses were conducted using baseline and weekly data to estimate relationships between respondent characteristics and subsequent pregnancy scares. Event history methods were used to assess pregnancy scares as a predictor of unintended pregnancy. RESULTS: Nine percent of the young women experienced a pregnancy scare during the study. African-American race, lack of two-parent family structure, lower GPA, cohabitation, and sex without birth control prior to the study are associated with experiencing a pregnancy scare and with experiencing a greater number of pregnancy scares. Further, experiencing a pregnancy scare is strongly associated with subsequent unintended pregnancy, independent of background factors. Forty percent of the women who experienced a pregnancy scare subsequently had an unintended pregnancy during the study period, relative to only 11% of those who did not experience a pregnancy scare. CONCLUSIONS: Young women from less advantaged backgrounds are more likely to experience a pregnancy scare, and pregnancy scares are often followed by an unintended pregnancy.