The Dynamics of Transaminase and Alkaline Phosphatase Activities in the “Mother–Placenta–Fetus” Functional System

<b>Background:</b> The timing of delivery depends on the condition of the fetus and the mother's body, which is reflected in both the incretion of enzymes in the pregnant woman's body and their use by the developing fetus in the anabolic process. <b>The aim:</b> This work was aimed to analyze the activities of transaminases (aspartate aminotransferase (AST) and alanine aminotransferase (ALT)) and alkaline phosphatase (AlPh) in liquid media (blood serum, amniotic fluid, umbilical cord blood, and placental homogenate) in pregnant women in each trimester of pregnancy and in the postpartum period, considering the timing and type of delivery (term, premature or late delivery, or cesarean section). <b>Methods:</b> Data from studies in non-pregnant (n = 45) and pregnant (n = 193) women, including women in labor with different delivery timings (term, premature, and late) and types of delivery (natural birth or cesarean section), were analyzed. Amniotic fluid, umbilical cord blood, and the placental homogenate were collected during labor. The de Ritis coefficient (AST/ALT) was calculated. Alkaline phosphatase activity was determined using the standard constant-time method using Lahema diagnosticum biotests, and transaminase activity was determined using the colorimetric dinitrophenylhydrazine method, according to Reitman and Frenkel. <b>Outcomes:</b> The highest alkaline phosphatase activity was recorded in the placenta homogenate (6906.2 ± 208.1 U/mL) in pregnant women who gave birth at term. The highest transaminase activity was found in umbilical cord blood and, in particular, in the placenta in pregnant women with premature and late births. <b>Conclusions:</b> The significant role of transaminases and alkaline phosphatase in the transport functions of the histohematic barriers of the mother and fetus was established, which provides a mechanism for the constancy of enzyme levels in blood plasma.