Amniocentesis and chorionic villus sampling

Amniocentesis (taking of amniotic fluid) and chorionic villus sampling (biopsy from the placenta) are invasive methods for the monitoring of fetal chromosomes.

The chorionic villus sampling is performed by the 11th week of the pregnancy. Under ultrasonographic guidance a fine needle enters the placenta and takes material (Chorionic Villus)

Similarly, amniocentesis is performed by the 16th week. Under ultrasonographic guidance a fine needle enters the amniotic bag and takes amniotic fluid.

With both these two methods the number and integrity of chromosomes is examined and major abnormalities, such as Down’s syndrome, are excluded. However, this screening is not possible to rule out all abnormalities and a normal test result does not guarantee the birth of a healthy child. In both amniocentesis and chorionic villus sampling there is small risk of miscarriage (about 1%).