The hydrolytic activity of biological fluids in the maternal-placental-fetal unit is of maternal origin. Due to the incretion of enzymes from the digestive glands to blood, there is their further body distribution and transport across the blood-tissue barriers (including across the maternal-placental unit) into the amniotic fluid that is swallowed by the fetus and serves as a source of nutrients and hydrolases for its amniotropic nutrition. The proteolytic, amylolytic, alkaline-phosphatase, and lipolytic activities of hydrolases were studied in the serum, saliva, urine, and amniotic fluid in the first, second, and third trimesters in 86 pregnant women who had a full-term baby, in 34 pregnant women who had a premature baby, and in 31 with delayed delivery. A control group included 45 non-pregnant apparently healthy women. The levels of hydrolytic enzymes in the test biological fluids were found to depend on the length of labor. All the groups of pregnant women showed the enhanced serum activities of amylase, alkaline phosphatase, and lipase from the beginning to end of pregnancy, as well as multidirectional changes in pepsinogen depending on its urinary excretion.