Preterm birth before the 37th gestational week is most frequently caused by infection. The agents are aerobic and anaerobic bacteria. Infection usually ascends from the vagina. Microorganisms entering the choriodecidual space induce pro-inflammatory cytokines, which trigger prostaglandin synthesis and contraction activity of the uterus. Cytokines can also release proteases, which cause premature outflow of the amnionic fluid. Screening of vaginal infections is indicated in all cases of imminent preterm parturition and in the group of risk pregnancies. Screening on Streptococcus B is indicated to all pregnant women in the gravidity weeks 35 to 37. Beside streptococcus infections with the risk of disease of the neonate being 2 to 3 per 1000 of vital newborns, bacterial vaginosis caused by Gardnerela vaginalis is frequently diagnosed. Effective treatment of symptomatic cases of the advanced pregnancy is five days long administration of Metronidazol or Clindamycin - vaginal crème. Another frequent cause of the preterm birth is chlamydial infection. The best contemporary treatment is Azitromycine for five days. Therapy of women without symptoms of the imminent preterm parturition does not decrease its occurrence. It is therefore not recommended as well as is not recommended the therapy of pregnant women with asymptomatic bacterinuria. Beside the classical cultivations, detection of antibodies, DNA analysis and serum infection markers (leucocytes, C-reactive protein), detection of pro- inflammatory cytokines in the serum and in the vaginal secret (IL-6,IL-8,TNFα etc.) are used to diagnose vaginal infections.

        Key words: vaginal infection, screening, preterm birth.