The author in this work deals with the impact of infections on perinatal mortality and morbidity including possible mechanisms causing harm to pregnancy and preterm labour or miscarriage. There are stated the most frequent nosological units causing genital and extragenital infections together with laboratory parameters and clinical signs usable for early diagnosis of infections. The possibilities of monitoring vaginal biocoenosis and early diagnostics of dysmicrobia or subclinical vaginal infections are taken into consideration. There are stated recommended examinations for screening infections in pregnancy. This work refers to a programme for prevention of preterm labour in Germany performed by pregnant women through a pH-self measurement and it underlines the possibility of application of probiotic bacteria upon vaginal pH alteration.