The aim of this study was to determine the relationship between the morpho-funclional features of placentas from preterm births (PBs) with the results of bacteriological examination of the discharge from the cervical canal in women with spontaneous preterm birth (SPB). The study included 227 pregnant women at gestational age between 28 and 36 weeks and 6 days, who underwent examination in the period from 2017 to 2018. Depending on the gestational age. they were divided into 3 groups. In general. a strong relationship was found between the presence of pathological changes in placentas and the presence of opportunistic flora in women (R=0.722, P<0.001). The constructed mathematical models make it possible to determine, with a high degree of certainty, the main bacteria for all the studied groups of pregnant women, thereby identifying the risk group of women at the stage of pregnancy planning, predicting complications and increasing the possibility of deliver a full term baby.