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PH of amniotic fluid at physiological birth
Last reviewed: 23.04.2024
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Studies of the pH of amniotic fluid were conducted in 160 maternity wards during the normal course of the birth act. The duration of labor in primiparous animals was 12 h 42 min + 31.7 min, in repetitious 6 h 05 min ± 4.85 min. The evaluation of newborns according to the Angar scale was 7-10 points. In% of women at birth, the pH was recorded from the moment of the passage of amniotic fluid or the opening of the fetal bladder in the absence of labor.
To determine the pH value of amniotic fluid, the following groups were identified: 1st - absence of labor activity; 2nd - opening of the uterine throat 1-3 cm; 3rd - 4-5 cm; 4th - 6-8 cm; 5-th - 9-10 cm; 6th group - II period of childbirth.
It was established that the pH values of amniotic fluid fit into the parameters characteristic for liquid biological media of the human body. In the course of the generic act, as the delivery progresses and the opening of the uterine throat progresses, the pH of the water gradually decreases, which indicates the depletion of their buffer capacity.
Thus, the pH of amniotic fluid in 6 groups was, respectively: 7.36 ± 0.005; 7.32 ± 0.008; 7.30 + 0.006; 7.27 ± 0.006; 7.23 ± 0.01 and 7.04 ± 0.04.
Intra-hourly fluctuations of water pH: 0.02 ± 0.0005; 0.02 ± 0.0006; 0.019 ± 0.0007; 0.02 ± 0.0007; 0.03 ± 0.01.
The most significant decreases in pH values are observed at the onset of labor, as well as at the end of the disclosure period and in the second stage of labor. Apparently, it is at these moments of the birth act that the fetus experiences increased stresses, releasing acidic metabolic products into the amniotic fluid. Thus, in the second group, the load on the fetus is associated with the transition of the uterus from the state of functional rest to the working regime, in the 5th and 6th groups - due to the fetal movement along the birth canal with compression of the presenting part. It should be specially emphasized that the small value of the mean error of the arithmetic mean (M) indicates the stability of the indicators.
The value of intrachassis fluctuations in the pH of amniotic fluid was 0.02 and did not change during the opening of the uterine throat. When calculating the reliability criterion, the difference between significant differences between the groups studied was not revealed, which indicates a small deviation of the pH values of the water from the mean value in the course of normal births. The reliability of the difference in the pH values of the water in the study groups is as follows: the difference between the 1 st and 2 nd groups is reliable, between 2 nd and 3 rd - not significant, between the others - the high reliability of the difference in indices was revealed.
The greatest changes in the pH of amniotic fluid in the II period may indicate a maximum load on the fetus and correspond to the development of fetal physiological acidosis in the fetus.
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