Prenatal diagnosis is an examination that is carried out in order to detect congenital or hereditary defects in the unborn child. This examination includes several components: chorionic villus sampling, amniocentesis and a comprehensive ultrasound.
Women with an increased risk of having a child with a congenital disease, are offered prenatal diagnosis. Risk factors include maternal age (over 36 years), a combination test that indicates an increased risk of defects and genetic chromosomal aberrations in the family.
With chorionic villus sampling can be checked if a baby has a chromosomal aberration, such as Down’s syndrome. Chorionic villus sampling can take place in the period from 11 to 14 weeks of pregnancy.
With amniocentesis, the number and form of the chromosomes can be determined. Metabolic diseases can also be detected by means of various tests. Amniocentesis can be performed after 15 weeks of pregnancy.
A comprehensive ultrasound examination can take place when defects are shown in the 20-weeks ultrasound. This is to ascertain whether the child grows sufficiently, how the child’s organs are developing and whether there is enough amniotic fluid.
In chorionic villus sampling, a small piece of placenta tissue is removed via the abdominal wall or via the vagina. This tissue looks flaky. The cells of the flakes are analyzed in the laboratory for defects in the chromosomes.
In amniocentesis, amniotic fluid is sucked up through the abdominal and uterine wall. The amniotic fluid contains cells from the unborn child. These cells can be analyzed in the laboratory.
In a comprehensive ultrasound examination, blood flow speed in the blood vessels of the uterus and of the child may be measured. This is called Doppler ultrasound.