Objectives: To conduct new research that prospectively assesses fertility intentions and pregnancy attitudes using waves of data from a national sample of US women. This work will fill a gap in the growing body of research on these topics by providing insights into the extent to which US women’s fertility intentions change over time and how this corresponds with contraceptive use. Methods: Panel data from a national sample of 2,353 nonsterilized US women aged 18 to 39 years were gathered at three points in time between 2012 and 2013. These were used to examine two outcomes: stability and fluctuations in attitudes reflecting uncertainty about having children and associations between pregnancy attitudes and consistent contraceptive use. Results: Although 39% of the sample reported uncertain fertility intentions on at least one survey, only 9% were uncertain at all three. Thus, while many women are unsure they want to have children at any one point in time, this outlook appears to be a short-term one. The second study found that 53% of women indicated it was very important to avoid pregnancy, but only 23% would have been very unhappy to be pregnant. In logistic regression models, only pregnancy avoidance was associated with consistent contraceptive use. Pregnancy avoidance was less likely to change over time, and change in pregnancy avoidance, but not happiness, was associated with changes in consistent contraceptive use. Conclusion: Many women’s pregnancy attitudes change over a short period of time, and health care providers should assess these outlooks on a regular basis.