During pregnancy due to hormonal changes the mother is increasingly sensitive to microbiological infections that can also activate infections latent until the beginning of pregnancy. Pathogenic agents are those corresponding to microorganisms as before pregnancy, but the course of disease can be more complicated. The most serious infections can threaten not only the mother’s health but also a developing foetus. There particularly belong the microorganisms invading into the mother’s bloodstream and transplacentally into foetal tissues or the infection is localised at the vaginal mucosa, in the uropoetic system and can be ascendingly spread and can cause bacterial inflammation of amnions and both maternal and foetal infections. Microbiological diagnostics of an infectious disease of the mother is performed similarly as to any other patient. Targeted screening microbiological examinations are directed particularly at those infections threatening not only the mother’s health but also the healthy development of the foetus, or they are specific only for the period of pregnancy.