The puncture of the amniotic liquid (amniocentesis) is used like the chorion sampling to examine the unborn child for deformation of the chromosomes.
Deformations of the chromosomes can cause genetic illnesses. The risk of having a child so afflicted is higher with pregnant women over 35 years of age or if there is a familial disposition for genetic illnesses.
For this examination, some amniotic fluid from the pregnant woman is extracted through the abdominal wall between the 14th and the 18th week of pregnancy. The child’s cells are contained in the amniotic fluid and are examined over a two week period in order to observe the number and structure of the chromosomes.
Amniocentesis has a risk for miscarriage of 1%.