Amniotic fluid

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Amniotic fluid or amniotic fluid is called by the amnion as the innermost caul the amniotic sac clear, aqueous formed body fluid with which the amniotic cavity is filled. The amniotic fluid, like the amnion, belongs to the tissue of the abdominal fruit, not to the maternal tissue, but it contains parts of the maternal blood.

As early as the 4th week of pregnancy , the amniotic fluid surrounds the human embryo in such a way that adhesions with the amniotic skin are prevented. Later it also serves as a shock-buffering protective cushion and enables the growing fetus to move weightlessly. It assumes a further function in the opening phase of childbirth by supporting the widening of the cervical canal as a hydrostatic wedge - if the amniotic sac is intact .

The amount of amniotic fluid is checked during preventive examinations of the pregnant woman: In the 10th week of pregnancy there are usually around 30 milliliters (ml) of amniotic fluid, around 400 ml in the 20th week of pregnancy, around 1000 ml in the 30th to 34th week of pregnancy, around 800 at birth ml. An increase in the amniotic fluid to 1500–2000 ml is called polyhydramnios , a decrease to less than 200–500 ml is called oligoamnion or oligohydramnios . The difference to the norm can be compensated for by amniotic drainage or amniotic infusion (symptomatic therapy). The amount of amniotic fluid is measured, for example, sonographically with the amniotic fluid index .

The amniotic fluid is absorbed by the fetus, which, towards the end of pregnancy, drinks around 400 ml of it daily. This proportion of the volume is absorbed by the fetal intestine and initially passed on to the maternal bloodstream mainly via the placental circulation. As the kidneys develop, an increasing proportion is released back into the amniotic sac as fetal urine. Since the placenta takes on the actual excretory functions, the urine that the fetus empties into the amniotic fluid is not very concentrated. But its amount is important because it will later make up the largest proportion of the amniotic fluid produced. If, for example, too little urine is produced due to a malformation in the fetal urogenital tract , this can mark the beginning of the so-called oligohydramnios sequence (formerly: Potter sequence ): The amniotic sac contains too little amniotic fluid, which leads to malformations of the skull and face and displaced hips , Malformations of the feet (such as club feet ) and pulmonary hypoplasia can occur.

Conversely, polyhydramnios develop if the fetus does not drink enough and if the placental supply is undisturbed, urine production is not reduced. This can occur as a result of an obstruction to the fetal gastrointestinal passage, e.g. B. in an esophageal atresia or a weak swallowing reflex .

Various hereditary diseases and chromosomally related peculiarities can be detected by prenatal diagnosis when amniocentesis is used to remove and examine amniotic fluid. An unusual amount of amniotic fluid can be used as a sonographic soft marker for certain peculiarities.

If a large amount of amniotic fluid enters the maternal circulation, an amniotic fluid embolism can occur, a rare but dramatic obstetric emergency situation.

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Wiktionary: amniotic fluid  - explanations of meanings, word origins, synonyms, translations