- Amniocentesis (AMC) – collection of amniotic fluid
- Collection of chorio villi (CVS)
- Collection of umbilical blood (PUBS)
The amniotic fluid (VP) is a clear yellow liquid containing both free biochemical substances and living cells of the foetus. Most often the collection is performed in about 16th week of pregnancy. However, it is possible to carry it out safely already from the completed 14th week of pregnancy (it is counted from the first day of the last menses, or more accurately according to the ultrasound examination). AMC can also be performed at later stages of pregnancy; however, the interpretation of the results is somewhat weakened due to the limited possibility of an intervention into the course of pregnancy after 24th week.
The reason for AMC is, most often, the cytogenetic (chromosomal) examination of the cells of the foetus. Within the biochemical examinations of the fluid there is most often the determination of values of the protein called alphaphetoprotein under a suspicion of spina bifida. In justifiable cases the appropriate genes are examined by means of methods of molecular genetics.
The collection is performed under the control of ultrasound with a very thin needle (ca. 0.5 mm in diameter). During the period of collection the doctor can clearly see the needle tip, therefore an injury to the foetus is very improbable. The pregnant women describe the feeling of slight pain similar to the case of blood collection or during application of a common injection. About 15-18ml VP is collected. The foetus fills in this dispensable quantity during several hours following the collection.
With respect to the fact that the amniocentesis is accompanied with certain risks, there must be a clear reason for its performance.
The risk of pregnancy complications connected to the collection of VP is, according to literature sources, ca. 0.5 to 1%. At the same time it depends on the initial reason of the amniocentesis.
If there is a reason, it is possible, instead of AMC, to perform a collection of other tissues of the foetus – for example, the collection of a part of chorion (tissues from which the placenta is formed) - CVS, or the collection of a small quantity of the umbilical blood (PUBS).
CVS is performed at early stages of gravidity - during 9th – 13th week - with a risk comparable to the AMC. Within this age stage of pregnancy it is possible to perform an early amniocentesis (EAC) as well, although the risks of this intervention are, according to literature, slightly higher than in the case of AMC, or CVS. The quality of chromosomal examination from cells obtained by CVS or EAC may be lower than of those obtained by AMC.
In case of a fast examination with a method of AmnioPCR, the result is known within 24 hours from the collection. The result of a complete chromosomal examination (caryotype) lasts ca. 2 weeks.
PUBS can be technically performed from about 16 th week. This performance is burdened with a risk until 30th week, this risk being comparable to the AMC. However, this procedure is technically slightly more demanding. The result of PUBS is, however, available in a couple of days.
All these performances mostly utilize similar techniques under UZ control, as the AMC.
All these performances are performed in an outpatient manner and after them we recommend to reduce physical work for a few days; a pregnant woman has a claim for one week a disability of work.