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amniotic fluid[¦am·nē¦äd·ik ′flü·əd]
fluid that surrounds the fetus of higher vertebrate animals (including man) while developing in the mother. It fills the gestation sac formed by the fetal membranes. The Russian scientist K. N. Vinogradov found in 1871 that this fluid is produced by the secretion of the amnion. It is a light transparent liquid containing albumin, fat, sugar, sodium chloride, urea, hormones, and radioactive substances, which contribute to the production of energy for rapid growth and development of the fetus. The amount of amniotic fluid varies with the time of pregnancy—from 300 milliliters at the beginning to 1.5 liters at the end.
Amniotic fluid prevents the skin of the fetus and the amnion from coming into contact and fusing; enables the fetus to move actively, which is necessary for its development; protects the umbilical cord and placenta against pressure from the large parts of the fetus; influences the position of the fetus and the location of its parts; protects the fetus against external injuries; helps to open the mouth of the uterus during childbirth; and contributes to the distensibility of the uterus and normal course of labor. In severe gestational toxicoses, cardiovascular diseases, diabetes mellitus, and so forth hydramnios, or excess of amniotic fluid (more than 2 liters), may arise and cause extreme distension and attenuation of the uterine walls, which can sometimes lead to an abortion or incorrect position of the fetus. An insufficiency of amniotic fluid owing to inadequate secretory activity of the amnion prevents the fetus from developing normally. A premature effusion of amniotic fluid may result in an abortion.
REFERENCESKuntsevich, A. N. Okoloplodnye vody kak toniziruiushchee i lechebnoe sredstvo v akusherstve. [Ivanovo] 1937.
Vinogradova, S. P. O biologicheskom znachenii okoloplodnykh vod. Kiev, 1928.
A. E. SAVASTENKO