Background: Cesarean section performed in the absence of medical indication is of concern in many countries, but studies focusing on its prevalence are inconclusive. The objective of this study was, first, to describe the prevalence of cesarean section without medical reason in terms of the diagnostic code listed in the Swedish Medical Birth Register, and to assess its contribution to the general increase in the number of cesarean sections; and second, to study regional differences and differences in the maternal characteristics of women having a cesarean birth with this diagnostic code. Methods: Birth records of 6,796 full-term cesarean sections in two Swedish regions with the diagnostic code O828 were collected from the Swedish Medical Birth Register. Descriptive data, t test, and logistic regression analysis were used to analyze data. Results: The rate of cesarean sections without medical indication increased threefold during the 10-year period, but this finding represents a minor contribution to the general increase in the number of cesarean sections. The diagnostic code O828 was more common in the capital area (p < 0.001). Secondary diagnoses were found, the most frequent of which were previous cesarean section and childbirth-related fear. Regional differences existed concerning prevalence, classification, maternal sociodemographic, obstetric, and health variables. Conclusions: The rate of cesarean sections without medical reasons in terms of the diagnostic code O828 increased during the period. The prevalence and maternal characteristics differed between the regions. Medical code classification is not explicit when it comes to defining cesarean sections without medical reasons and secondary diagnoses are common. (BIRTH 37:1 March 2010).