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The state of the acid-base state of fetal blood at physiological birth
Last reviewed: 20.11.2021
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The data of the literature testify to the undoubted dependence between the state of the newborn and the parameters of the acid-base state of its blood, therefore, when determining the fetal condition during childbirth, the results of the analysis of blood taken from the skin of its head are crucial, and the acidosis can be recognized at any stage of childbirth . The possibility of taking fetal blood to determine the main parameters before birth is one of the most significant achievements of midwifery in recent years. The production of Zaling's sample is possible only with sufficient opening of the uterine throat, not less than 4-5 cm.
In the study, in all women in labor during normal delivery, Zaling's test was performed 3 times during the delivery process - in the 3rd, 4th and 6th groups. In the 6th group, blood was collected from the umbilical vein at the time of the birth of the child before the first inspiration. In a number of cases, Zaling could also be tested with a shortened cervix in the absence of labor, but a small number of observations did not allow the mathematical processing of data. Blood from the finger of the parturient to determine the components of the acid-base state was taken simultaneously with the blood sampling from the presenting part of the fetus. Investigation of the components of the CBS was performed immediately after the material was collected by the micro-method on the micro-Astrop instrument with the following CBS parameters: current pH, deficiency (excess) of bases - BE, buffer bases - BB, standard bicarbonates - SB and partial pressure of carbon dioxide - pCO 2.
At physiological birth and normal state of the fetus, the parameters of the acid-base state of its blood are within the normal range. In the process of the generic act, a decrease in the actual blood pH in the second stage of labor is noted, an increase in the deficiency of bases, a decrease in the number of buffer bases and standard bicarbonates, and an increase in the partial pressure of carbon dioxide. All components of the acid-base state of fetal blood significantly differ in the 4th and 6th groups. There were no significant differences between the indices of the 3rd and 4th groups.
The data presented indicate that, with a favorable course of the birth act and the physiological state of the fetus, no significant changes in fetal metabolism occur in the opening period and only in the second stage of labor there is a significant decrease in pH, an increase in the deficiency of bases, a decrease in the number of alkaline components and an increase in the partial pressure of carbon dioxide , indicating the development of compensated metabolic acidosis.
The study of the components of the acid-base state of the mother's blood in the dynamics of the birth act did not reveal any significant changes indicating the depletion of the buffer capacity of the blood. In all the study groups, the parameters of the acid-base state of the mother's blood are within physiological limits. Mathematical analysis revealed a significant reduction in the quantities of buffer bases, standard bicarbonate and pCO 2 in the 6th group compared to 4 minutes, but these fluctuations are within physiological.
The presented data do not give an opportunity to judge the presence or absence of a link in the changes in the components of the acid-base state of fetal and maternal blood.