The aim of the study is to identify forms of morphofunctional insufficiency in the developing components of the placenta in spontaneous abortions in early pregnancy, and to propose a new classification. Material and methods. A study was conducted of the scrapings and blood samples from the uterine cavities of 30 patients who experienced sudden miscarriage between 5—12 weeks of gestation, and of 30 patients with physiologically progressing pregnancies interrupted by surgical abortion. Pathomorphological studies of endometrial biopsies, immunohistochemical analyses of vascular endothelial (VEGFA) and transformative (TGF-β2) growth factors in chorionic villus and stromal endometrial cells, and immunodiffusion analysis of glycodelin content in the uterine blood from the day of uterine evacuation were performed. Results. In spontaneous abortions in early stages of gestation, structural changes were revealed. They were manifested by delayed growth and villous differentiation, superficial invasion of the non-villous trophoblast, reduction of the villous trophoblast, incomplete differentiation of stromal cells, incomplete secretory transformation of glands, insufficient conversion of spiral arteries, as well as functional disorders, including imbalance of vascular-endothelial and transforming growth factors, and low content of glycodelin in the blood from the uterine cavity. These observations lead to the identity of three forms of structural and functional insufficiency in the early stages of placental development: trophoblastic, endometrial and mixed. Conclusion. Diagnosis of selected forms of structural and functional insufficiency of the forming placenta in early stages of gestation is necessary in obstetric and gynecological practice to identify the causes of early reproductive mortality, and for pregravidary preparation in the planning of subsequent pregnancy.