Background: Unwanted pregnancies and their complications are one of the major problems facing women in the world. This study aimed to determine the factors that affect unwanted pregnancy in the population covered by the Shahroud University of Medical Sciences in ۲۰۱۳.Methods: In this case-control study, ۱۱۶ cases and ۲۵۱ controls were randomly selected from those who referred to health care centers and they were studied. The data were analyzed using Univariate and multivariate logistic regression analysis.Results: The mean age of the participants was ۲۷.۶±۵.۸ years and the average age of husbands was ۳۱.۸ ± ۶.۲ years. Average number of parity was ۱.۲ ± ۱.۲ and the number of children born alive was ۱.۲ ± ۱.۱ and the average distance between the last and the current pregnancy (interval birth) was ۳۲.۴ ± ۳۷.۷ months. Multivariate analysis of the data from the final model of the study showed that the use of non-secure methods of pregnancy prevention, rural residence, low education of the mother and the age of the last living child were the main risk factors of unwanted pregnancies (P <۰.۰۵).Conclusions: Encouraging qualified women to make use of reliable contraceptive methods specially more permanent methods and encouraging them to get the contraceptive devices from health care units with emphasis on proper training and regular retraining of clients, paying more attention to awareness raising of women in rural areas, and having appropriate birth spacing can be effective in reducing unwanted pregnancies.Background: Unwanted pregnancies and their complications are one of the major problems facing women in the world. This study aimed to determine the factors that affect unwanted pregnancy in the population covered by the Shahroud University of Medical Sciences in ۲۰۱۳. Methods: In this case-control study, ۱۱۶ cases and ۲۵۱ controls were randomly selected from those who referred to health care centers and they were studied. The data were analyzed using Univariate and multivariate logistic regression analysis. Results: The mean age of the participants was ۲۷.۶±۵.۸ years and the average age of husbands was ۳۱.۸ ± ۶.۲ years. Average number of parity was ۱.۲ ± ۱.۲ and the number of children born alive was ۱.۲ ± ۱.۱ and the average distance between the last and the current pregnancy (interval birth) was ۳۲.۴ ± ۳۷.۷ months. Multivariate analysis of the data from the final model of the study showed that the use of non-secure methods of pregnancy prevention, rural residence, low education of the mother and the age of the last living child were the main risk factors of unwanted pregnancies (P <۰.۰۵). Conclusions: Encouraging qualified women to make use of reliable contraceptive methods specially more permanent methods and encouraging them to get the contraceptive devices from health care units with emphasis on proper training and regular retraining of clients, paying more attention to awareness raising of women in rural areas, and having appropriate birth spacing can be effective in reducing unwanted pregnancies.