OBJECTIVE To determine the prevalence of sexually transmitted infections (STIs) among women attending an antenatal clinic in urban China and to show whether reported symptoms and findings on clinical examination predicted STIs in this population. METHODS Cross-sectional descriptive study was conducted among 504 pregnant women attending an antenatal clinic in Fuzhou, China. Structured questionnaires were used to collect demographic and behavioral information, and clinical and gynecologic examinations were performed to detect clinical signs of STIs. Blood samples, vaginal swabs, and cervical swabs were collected, respectively, to test for antibodies to syphilis, culture Trichomonas vaginalis (T. vaginalis), and perform PCR to detect Chlamydia trachomatis (C. trachomatis) and Neisseria gonorrhoeae (N. gonorrhoeae). RESULTS C trachomatis was detected in 51 (10.1%), N gonorrhoeae in 4 (0.8%), T vaginalis in 16 (3.2%), and syphilis in 1 (0.2%) of the 504 pregnant women. Fifty-two (73%) of 71 women with any STI were asymptomatic. Multiple logistic regression analysis indicated that age <or=25 years (OR=2.72) and monthly income >RMB 2000 yuan (OR=3.57) were significant independent risk factors for chlamydial infection (P<0.05). The reported symptom of vaginal discharge or the clinical sign of either vaginal or cervical discharge poorly predicted infection with C trachomatis, N gonorrhoeae, or T vaginalis, with a positive predictive value <25% for each STI. CONCLUSIONS A substantial prevalence of STIs, including a large proportion of asymptomatic infections, was found among pregnant women in the study area. These results support a strategy of screening pregnant women for bacterial STIs (followed by treatment of infections), which could be integrated into routine pregnancy care in China.