Amniotic fluid

Amniotic fluid is called by the amnion ( amniotic sac ) formed a clear, aqueous body fluids with which the amniotic cavity has been filled. The amniotic fluid is as much as the amnion to own tissues of the fetus, not to the maternal tissue.

In the fourth week of pregnancy, to surround the human embryo already completely and prevents adhesions thereof to the amnion. Later, it also serves as a " protective cushion ", which helps absorb shocks and allowing the growing fetus movements. A fourth function takes in the opening stage of labor by - as it supports the widening of the cervical canal as a hydrostatic wedge - with intact amniotic sac.

The amount of amniotic fluid is checked at every screening of pregnant women: In the 10th week of pregnancy amniotic fluid are usually about 30 milliliters (ml ) present in the 20 to 350 ml, in the 30th to 34th week about 1000 ml, birth about 800 ml an increase of the amniotic fluid to 1500-2000 ml is called polyhydramnios ( therapy: Amniondrainage ), a reduction to less than 200-500 ml as Oligoamnion or oligohydramnios ( therapy: Amnioninfusion ). The amount of amniotic fluid is measured, for example, by sonography with the amniotic fluid index.

The amniotic fluid is completely renewed every three hours, with the fetus at the end of pregnancy, of which about half, ie 400 ml drinks. This proportion is largely absorbed by the fetal intestine and delivered partly through the placental circulation in the maternal bloodstream. The urine, which emptied the fetus into the amniotic fluid, little is concentrated, due to these excretory function of the placenta, for the development of the fetus but is of crucial importance since it quantitatively has the largest share in the production of amniotic fluid: If, because of, for example, a malformation in fetal urogenital tract produces too little urine, this represents the beginning of the so-called oligohydramnios sequence (formerly Potter sequence ) represents: the amniotic sac contains too little amniotic fluid, leading to malformations of the skull and face, displaced hips, deformities of the feet (eg. formation of clubfeet ) and hypoplasia ( underdevelopment ) of the lungs leads.

Conversely, it is the formation of polyhydramnios, if as a result of obstruction of the fetal gastrointestinal passage such as a atresia of the fetus insufficient drinking, urine production is not reduced due to the undisturbed placental supply.

Various genetic disorders and chromosomal related special features can be described by prenatal diagnosis, eg by means of amniocentesis and subsequent amniocentesis prove. An unusual amount of amniotic fluid can be regarded as sonographic soft markers for certain features.

At a crossing of a larger amount of amniotic fluid in the maternal circulation may lead to an amniotic fluid embolism, a rare but dramatic obstetric emergency situation.