BACKGROUND The aim of this study was to evaluate the frequency of bacteriuria in pregnant women referred to the medical centers of Tabriz, Iran, for prenatal care. METHODS A total of 1100 healthy pregnant women who were referred to 50 medical centers in Tabriz for a regular prenatal care were evaluated for bacteriuria. RESULTS The frequency of asymptomatic bacteriuria was 6.1%. Maternal age was lower in the women with a positive urine culture (P=.02). Asymptomatic bacteriuria had no relationship with gestational age, parity, level of education, and body mass index. CONCLUSIONS We found a relatively high rate of bacteriuria in our cohort of asymptomatic pregnant subjects, especially the younger ones. For prevention from the complications of the asymptomatic bacteriuria in pregnant women, such as pyelonephritis, hypertension, preeclampsia, low birth weight, prematurity, septicemia, and even maternal and neonatal death, it is recommended to perform urine culture as a routine evaluation during the pregnancy.