During pregnancy amniotic fluid surrounds the baby, protecting it from pressure, and maternal tissue from fetal movements. This liquid also acts as a heat insulator and contributes to the optimal development of various body structures of the unborn child.
Amniotic fluid fills the amniotic cavity, which develops during the first few weeks of pregnancy. This cavity is bounded by a membrane called an amnion. From the earliest stages of development, amniotic fluid is produced by amnion cells. Further, during the first trimester of pregnancy, their accumulation is associated with exudate of maternal plasma and the fetus circulating in the intermediate membrane spaces.
In the second trimester, before the twentieth week of pregnancy, the amniotic fluid has a composition and osmolarity comparable to that of the mother and fetus, whose skin is permeable to water, electrolytes, urea, and creatinine. After the twentieth week, amniotic fluid is found in the urine of the fetus, due to the maturation of its renal system.
During pregnancy, the fetus produces a large amount of sebum, which is necessary for the formation of the so-called primordial lubricant, the lipid layer of which protects the skin from maceration caused by amniotic fluid.
During the first two trimesters of pregnancy, the volume of amniotic fluid is much larger than the «volume» of the embryo. And in the last three months of pregnancy, the ratio between the two volumes decreases in favor of the fetus.
Analysis of amniotic fluid
In the amniotic fluid, various substances are in suspension, and their composition varies significantly, depending on the stage of development of the embryo. Amniocentesis - a puncture of the amniotic membrane, is carried out as a rule between 16 and 18 weeks of pregnancy with the aim of examining the amniotic fluid. At this stage, the cells of the epithelial tissues of the skin, lower urinary tract, trachea, etc., are located in the amniotic fluid, the culture of which allows us to examine the chromosome map of the unborn child and thereby make a prenatal diagnosis for the presence or absence of chromosomal abnormalities (for example, Down syndrome). The quantitative composition of alpha-fetoprotein in the amniotic fluid makes it possible to detect the presence of diseases and malformations, such as spina bifida, anencephaly, or meningocele.
Amniocentesis is performed using a thin needle under ultrasound guidance. Like any invasive procedure, amniocentesis has a certain risk of miscarriage, estimated at 0.5%. Therefore, there is no need to carry out such a check without serious reason.
Causes of polyhydramnios and oligohydramnios
An excessive amount of amniotic fluid is called polyhydramnios. It can be the result of multiple pregnancy, gestational diabetes or congenital malformations of the fetus, (for example, intestinal obstruction). Reduced amniotic fluid - oligohydramnios. This condition can be determined by placental dysfunction.
Recent scientific studies of foreign scientists have shown that amniotic fluid is an excellent source of multipotent stem cells that can differentiate into various tissues. These cells can be stored in special stem cell banks, in anticipation of major scientific discoveries, for which the future lies.