Background Chlamydia trachomatis causes the most prevalent bacterial Sexual Transmitted Infection. In pregnant women, untreated chlamydial infections are associated with abortions, premature rupture of membranes, postpartum endometritis, low birth weight and transmission to the newborn. In Có rdoba, Argentina, there is little knowledge about the prevalence of Chlamydia trachomatis in women in their third trimester of pregnancy, so, the aim of this study was to evaluate Chlamydia trachomatis prevalence and genotypes present in Cordovan pregnant women with different age and socioeconomic status. Methods and findings Design: prospective study. Settings: Women population from Cordoba city, Argentina. Population: Pregnant women having 35 to 37 weeks of gestation. Methods: Five hundred and nine cervical swabs were collected. Each sample was subjected to DNA extraction and PCR for Chlamydia trachomatis using primers NRO/NLO and CTP1/CTP2. Positives samples were sequenced to determine genotype. Main outcome measures: Demographic data of the patients were collected to detect a population at risk for this infection.