Objective: to study the dynamics of the microbiota of a freshly excreted middle portion of urine in primigravida at different times of all three trimesters of pregnancy.
Materials and methods. A single-center prospective observational cohort study was conducted with a consecutive enrollment of 30 women at different gestational ages: I – 8–12 weeks, II – 22–24 weeks, III – 30–32 weeks. A midstream specimen of morning vesical urine was taken for the study, then it was cultivated using nutrient media for aerobic and anaerobic microorganisms under appropriate conditions. Statistical analysis was performed using SPSS ver.26 (IBM SPSS Inc., Chicago, IL, USA).
Results. The freshly released middle portion of urine in all 30 observations in the I-III trimesters contains aerobic-anaerobic associations of microorganisms. Coagulase-negative staphylococci, Enterococcus spp., Corynebacterium spp., Lactobacillus spp., Eubacterium spp. prevail in the urine during pregnancy. The E. coli,
Candida spp. detection frequency decreases by the third trimester, but Lactobacillus spp. detection frequency rises. Significant differences in the detection frequency were found only in Propionibacterium spp. and Lactobacillus spp. The average level of bacteriuria in most cases is 102-103 CFU/ml with significant differences only in E. faecium, Lactobacillus, Propionibacterium spp. in the III trimester.
Discussion. The study of urine at different times of all three trimesters of pregnancy refutes the previous ideas about asymptomatic bacteriuria. The urine microbiota in primigravida during pregnancy has wide spectrum and quite stable until delivery. Such bacteriuria can be considered asymptomatic, but it is a consequence of a healthy state and it is not a disease or its predictor. Conclusion. The term asymptomatic bacteriuria is not correct in the context of risk factor of urinary tract infection in pregnant women.

Keywords: urine microbiota, pregnant women, asymptomatic bacteriuria