Premature birth is one of the leading problems of modern obstetrics, because, despite the efforts of scientists and practitioners, has no tendency to decrease. The stability of hemodynamic processes in the mother-placenta-fetus system is one of the basic conditions that ensures the normal course of pregnancy, growth and development of the fetus. Circulatory disorders in it leads to many complications of pregnancy. It has been established that using metabolic therapy in the form of omega-3 polyunsaturated fatty acids (PUFAs) in pregnant women helps to improve blood circulation in the mother-placenta-fetus system, improves the rheological properties of blood, prevents the development of preeclampsia and affects the reduction of perinatal complications. The introduction of Doppler studies of the blood flow of the placental complex (PC) into practical obstetrics allows not only to assess the condition of the fetus, but also to predict the development of possible complications.The aim of the study was to investigate the Doppler parameters of the state of the placental complex (PC) of pregnant women with the threat of preterm labor who received metabolic therapy.Material and methods of the study. The analysis of Doppler parameters of the state of the PC 60 pregnant women with the threat of preterm labor in the period of gestation 28-34 weeks was carried out. Pregnant women were divided into 2 groups: 1 group (n = 30) - pregnant women with the threat of preterm labor, who received standard complex basic therapy in combination with metabolic therapy in the form of 300 mg of omega-3 PUFAs per day, group 2 (n = 30) pregnant women with the threat of preterm labor, who received only standard complex basic therapy. The control group (CG) consisted of 30 practically healthy women with physiological pregnancy.The results of the study and their discussion. According to the Doppler study of PC, it was found that in 1 and 2 groups there was an increase in resistance index (IR) and systolic-diastolic ratio (SD) in the umbilical arteries (UA) (group 1: IR-0.87,80.05 and SD -3.57±0.2; group 2: IR-0.88±0.05 and SD-3.56±0.1) compared with pregnant CG (IR-0.62±0.07 and SD- 2.85±0.3). At the same time, indicators of IR, SD, pulse index (PI) and systolic peak velocity (SPV) in the middle cerebral artery (MCA) corresponded to thenorm, while in the fetal aorta (FA) an increase in IR and a decrease in PI (group 1: II- 1.05±0.2 and PI-0.9±0.2, group 2: IP-1.05±0.1 and PI-1.0±0.2) with unchanged indices of the SD and the average blood flow velocity (ABV). After the received treatment, in pregnant women of group 1, there were changes in Doppler hemodynamic parameters in UA and FA, namely: a decrease in IR and SD (II-0.69±0.2 and SD-2,98±0.2) in the UA and a decrease in IR and an increase in PI (IR-0.78±0.1 and PI-1.9±0.2) in FA compared with reliably higher data of Dopplerometric indicators of PC in pregnant women of group 2 (p±0.05).Conclusions. The use of metabolic therapy in the complex treatment of the threat of preterm labor has a positive effect on the change in the hemodynamic parameters of PC and can be used to improve blood flow in the mother-placenta-fetus system.