The objective: to study the prognostic significance of non-invasive markers of endogenous intoxication for determining the risk of premature rupture of membranes (PROM) at the gestation period of 26–34 weeks.Materials and methods. During the study the patients were divided into two groups: the 1st (main) group – 80 women with PROM at 26–34 weeks of pregnancy, and the 2nd (control) group – 50 women with a physiological course of pregnancy and term delivery without complications. The mean age of the examined women was 29.60±6.30 years. To determine the diagnostic value of the level of hematological indicators (concentration of leukocytes (WBC), granulocytes (GRAN), lymphocytes (LYM) in peripheral blood) and indices of endogenous intoxication (EI) as predictors of PROM and the initiation of preterm labor at a gestation period of 26–34 weeks, ROC-analysis was performed and the average quality of these prognostic factors was established (p<0.001).Results. The optimal cut-off point (cut-off value) for predicting PROM in preterm pregnancy according to the criterion of the maximum balance between sensitivity and specificity corresponded to WBC was more than 12.39/l, LYM – less than 19 %, GRAN – more than 76 %, NLR – more than 3.87, Kalf-Kalif’s leukocyte intoxication index (LII) is more than 3.42, Ostrovsky’s LII – more than 2.76. It was established that the area under the curve (AUROC) was 0.786 for WBC, 0.863 for LYM, 0.847 for GRAN, 0.866 for NLR, 0.753 for LII Ostrovsky, which testifies to the significant prognostic value of the studied predictors. Conclusions. The main non-invasive markers of the degree of activity of the inflammatory process and the severity of endogenous intoxication in premature birth with PRPO in pregnant women are: the total number of leukocytes, the level of granulocytes and lymphocytes, Kalf-Kalif LII and the neutrophil-lymphocyte ratio. In order to detect infectious markers of intra-amniotic infection and the further development of PROM and premature birth, it is recommended to calculate the level of endogenous intoxication in the second half of pregnancy using general blood analysis data on a hemolytic analyzer (WBC, GRAN, LYM, NLR).