Infectious diseases of the reproductive system are the most common cause of women’s visits to obstetricians and gynecologists. Possible pathogenetic agents of these diseases-viruses, fungi, bacteria and protozoa have different mechanisms of tissue damage at different levels and differently affect the reproductive health of the female population, leading to dramatic consequences for the mother and fetus. As a rule, up to 30% of infections are mixed, representing all possible combinations of pathogens, can occur in a subclinical form, complicate diagnosis and treatment and mutually aggravate the overall course of the disease. After the treatment of one infection, the manifestation of another may be noted, which is expressed in a clinical relapse and necessitates additional therapy. The urgency of the problem of the influence of infection on the pregnancy in the first trimester, its development, is explained by the high level of infectious morbidity of pregnant women, preceding and leading to the development of various obstetric pathology. Reproductive tract infections can account for up to 15% of early and up to 66% of late miscarriages. Available diagnostic tests in the daily practice of the doctor are insufficient to determine the overall picture of infection-related early gestational losses, and the treatment strategy of patients remains unchanged for a long time. Along with the well-known conclusions about the connection of some pathogens, such as chlamydia and gonococci with adverse pregnancy outcomes, there are «information gaps» in the evidence of the influence of opportunistic bacteria on the possibility of early spontaneous miscarriage. Available databases over the past ten years do not provide conclusive evidence linking pathological conditions such as bacterial vaginosis and aerobic vaginitis to early reproductive loss. Thus, new data are needed in determining the significance of individual microorganisms in the genesis of early miscarriages and timely elimination of potentially «managed» pregnancy losses. This review will examine in detail the pathogenetic features of some infections that are likely to be related to early reproductive losses.