Objective — to establish the connective tissue metabolic changes in amniotic fluid, which are characteristic of placental insufficiency in moderate and severe preeclampsia. Subject and methods. A study group consisted of 145 pregnant women with preeclampsia and placental insufficiency. Subgroup 1 included 98 patients whose pregnancy was complicated by placental insufficiency in moderate preeclampsia; Subgroup 2 comprised 47 patients whose pregnancy was complicated by placental insufficiency in severe preeclampsia. A control group included 52 apparently healthy women with physiological pregnancy. All the patients underwent routine clinical and laboratory examinations. The diagnosis of placental insufficiency was clarified by clinical, laboratory, ultrasound, cardiotocographic, and histological studies. The amniotic fluid taken during delivery was examined for connective tissue metabolic indices, such as free hydroxyproline, peptide-contained hydroxyproline, hyaluronidase, fucosidase, oligo-bound fucose, and protein-bound fucose. Results. The investigators established the increase in the number of metabolites of connective tissue biopolymers in amniotic fluid during delivery of patients, which is directly related to the severity of placental insufficiency and preeclampsia, suggesting that there is a rise in the intensity of connective tissue metabolic processes in preeclampsia and placental insufficiency. The rise in the concentration of free and peptide-bound hydroxyproline indicates the prevalence of catabolic processes in connective tissue by the time of delivery in pregnant women with placental insufficiency and moderate and severe preeclampsia. The changes in the level of carbohydrate components of glycoproteins, in particular, oligo-bound and protein-bound fucose and its enzymes-fucosidase and hyaluronidase in amniotic fluid at the time of delivery in pregnant women with placental insufficiency in moderate and severe preeclampsia are indicative of the destruction of the ground substance of connective tissue in these pregnancy complications. Conclusion. Quantitative shifts in the metabolic products of connective tissue biopolymers in amniotic fluid during delivery can serve as a diagnostic or prognostic criterion for determining the severity of placental insufficiency and preeclampsia.