BACKGROUND: The current investigation is a follow-up of a study on women's memory of childbirth, which showed that 60 percent made the same assessment of their overall birth experience at 1 year after delivery as they did at 2 months postpartum, and 24 percent had became more negative and 16 percent more positive. The study purpose was to gain some understanding of what factors make some women change their assessment over time. METHODS: Data from a longitudinal cohort study of 2,428 women who completed questionnaires in early pregnancy, at 2 months, and at 1 year after birth were analyzed. Two subsamples were studied: 1,451 women who said childbirth was a positive experience at 2 months and 151 who said it was a negative experience. Comparisons were made, within each sample, between those who made the same assessment at 1 year and those who had changed their view, with respect to psychosocial background, labor outcomes, infant health outcomes during first year, and experiences of intrapartum care. RESULTS: Changing the assessment from positive to less positive, mostly to "mixed feelings," was associated with difficult childbirth, such as painful labor and cesarean section; dissatisfaction with intrapartum care; and psychosocial problems, such as single status, depressive symptoms, and worry about the birth in early pregnancy. Changing the assessment from negative to less negative was associated with less worry about the birth in early pregnancy and a more positive experience of support by the birth-attending midwife. CONCLUSIONS: This study supported the view that measures of satisfaction with childbirth soon after delivery may be colored by relief that labor is over and the happy birth of a baby. More negative aspects may take longer to integrate. Supportive care may have long-term effects and may protect some women from a long-lasting negative experience.