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Introduction: Toxoplasmosis is one of the most common infectious diseases in the world and it caused by an intracellular protozoan called Toxoplasma gondii. This parasitic infection is usually asymptomatic in adults, but it become complicated if fetus infection occurred. This study aimed to determine the prevalence and incidence of toxoplasmosis in pregnant women in Babol, northern Iran. Materials and Methods: In this cross-sectional study during the years 2012-2013, 175 pregnant women in the first trimester of their pregnancy participated. Two ml blood was obtained from each participant and serum was separated. Then, anti-Toxoplasma antibodies were measured using ELISA method. Participants' demographic information and the risk factors were collected by questionnaire. Anti-Toxoplasma antibodies were measured in the second and third trimesters of pregnancy for who attended to the study. Results: The mean of age was 27.4 ± 9.5 years. 106 cases (60.6 %) had anti- Toxoplasma gondii antibodies (IgG) and 64 women (36.6 % ) had no specific antibody. The prevalence of infection was different in relation with age and location, but the difference is not statistically significant (p >0.05). Also, a statistically significant difference between prevalence of infection and other risk factors, such as abortion was not demonstrated. No case of acute Toxoplasma infection in the mother or congenital toxoplasmosis was reported. Conclusion: This study showed that over fifty percent of Toxoplasma infection occurs in twenty-five years of age. Furthermore, it showed that 36.6% of the studied population (pregnant women) was seronegative. Therefore, Toxoplasma infection should be screened in pregnant women in the first trimester of pregnancy in order to perform preventative measure of congenital toxoplasmosis.