Objective: to evaluate the perceptions of primiparous women about the effect of childbirth preparation classes on their childbirth experience. Design: descriptive qualitative study. Participants and setting: 13 Iranian women who participated in childbirth preparation classes and had a vaginal delivery were interviewed. Measurements: semi-structured interviews were used to collect data. Findings: six main themes were extracted from the data analysis: incentive and learning about pregnancy and childbirth; active participation in labour; sense of self-control; use of non- medical pain relief methods during labour; preferring vaginal birth to caesarean section; and positive childbirth experience. Key conclusions: women reported that participation in childbirth preparation classes prepared them well for a vaginal birth, and these classes were perceived to be associated with a positive childbirth experience. Implications for practice: attendance at childbirth preparation classes is perceived to have a positive effect on vaginal birth. Therefore, encouraging and supporting women to attend the full course of classes has the potential to increase women's preference towards vaginal birth, resulting in a reduction in the caesarean section rate.