What is the normal value of the maximum dark area of ​​amniotic fluid?

The normal value of the maximum dark area of ​​the amniotic fluid is an index that many pregnant women are concerned about. If it is not within the normal range, most pregnant women will become very nervous and anxious, because this means that the fetus in the abdomen is not in a normal state. If the amniotic fluid becomes turbid during the examination, it is very critical and must be treated in the early stage, otherwise the fetus will suffer from hypoxia.

In full-term pregnancies, amniotic fluid is contaminated with meconium in 12% to 22% of pregnancies. Clinical studies have shown that meconium contamination is related to fetal hypoxia and is therefore used as one of the diagnostic criteria for fetal distress. Secondly, it is believed that the excretion of meconium indicates the maturation of fetal gastrointestinal function under neural control. The third view is that the excretion of meconium is the result of umbilical cord traction stimulating the vagus nerve, which enhances gastrointestinal motility. The high incidence of meconium staining of the amniotic fluid and the low incidence of fetal acidemia and meconium aspiration syndrome support the latter two theories.

The degree of meconium contamination can be roughly divided into three categories:

Grade Ⅰ amniotic fluid is light green or light yellow and thin. It means that the fetus is suffering from chronic hypoxia and is in the compensatory period.

Grade II amniotic fluid is dark green, turbid, thick and contains fecal lumps. The fetus is in a period of acute hypoxia.

Grade III is dark brown, viscous and paste-like. The fetal skin, umbilical cord, fetal membranes, and placenta may all turn yellow. This is the subacute stage of hypoxia, with hypoxia lasting for at least 6 hours.

Amniotic fluid is the watery fluid that surrounds the embryo within the amnion. The amniotic fluid allows the embryo to move freely without pressing the uterine wall too tightly. Amniotic fluid also provides buoyancy. In addition, due to the high specific heat capacity of water, amniotic fluid can provide a constant temperature environment for the fetus, and amniotic fluid also lubricates the vagina during delivery.

The amnion begins to grow and become hydrated two weeks after fertilization. After another 10 weeks the fluid contains proteins, carbohydrates, lipids and phospholipids, urea and electrolytes. By mid-pregnancy, the embryo is breathing in the amniotic fluid and developing lungs and a gastrointestinal tract. When the amniotic membrane ruptures, some water will flow out of the body (commonly known as water breaking), but most of the water will remain in the uterus until the fetus is born.

98% of amniotic fluid is water, with small amounts of inorganic salts, organic hormones and shed fetal cells. The weight of amniotic fluid generally increases with the number of weeks of pregnancy. At 20 weeks, the average is 500 ml; at around 28 weeks, it increases to 700 ml; it is the highest at 32 to 36 weeks, about 1,000 to 1,500 ml; and then gradually decreases. Therefore, the clinical normal range is 300 to 2,000 ml. Exceeding this range is called "polyhydramnios", and failing to meet this standard is called "oligohydramnios". Both conditions require special attention.