Hypothesis/aims of study. Dysbiotic disorders of the vagina are one of the main risk factors of miscarriage. The analysis of vaginal microbiota during pregnancy in women having a history of miscarriage may contribute to understanding the importance of specific types of vaginal flora in the development of processes resulting in spontaneous abortion or preterm birth. This study was undertaken to evaluate the vaginal flora in the 1st trimester of pregnancy in women having a history of miscarriage.Study design, materials, and methods. To participate in the study, 160 individuals in the 1st trimester of pregnancy with and without a history of miscarriage were invited. Group 1 included 100 women with a history of miscarriage, group 2 consisted of 60 women without a history of miscarriage. The vaginal flora was analyzed with microscopic, bacteriological, and quantitative real-time PCR methods.Results. In patients with a history of miscarriage, the frequency of dysbiotic disorders of the vaginal flora was three times higher (11.0% and 3.3%) and pH value of the vaginal fluid was significantly higher. Along with a significant reduction of the proportion of the Lactobacillus flora in the 1st trimester of pregnancy in patients having a history of miscarriage, there was a significant increase in the abundance of opportunistic microorganisms, mostly aerobic flora, such as Enterobacteriaceae, Streptococcus spp., and Staphylococcus spp. Furthermore, there was a significant predominance of Ureaplasma spp. and Candida spp. in women with a miscarriage history.Conclusion. The vaginal microbiota in the 1st trimester of pregnancy in women having a history of miscarriage is characterized by higher pH values of the vaginal fluid, the prevalence of opportunistic microorganisms, a decrease in the abundance of the Lactobacillus flora, and a higher concentration of aerobic bacteria, Ureaplasma spp., and Candida spp. These findings indicate dysbiotic disorders of the vaginal microbiocenosis in women having a history of miscarriage, which can lead to late miscarriage and pretem birth. (For citation: Sinyakova AA, Shipitsyna EV, Budilovskaya OV, et al. Vaginal microbiota in the first trimester of pregnancy in women with a history of miscarriage. Journal of Obstetrics and Women’s Diseases. 2018;67(5):32-41. doi: 10.17816/JOWD67532-41).