Chromosomal disorders
The PrenaTest® can determine trisomies and other chromosomal disorders
If a certain chromosome is present in the cells of the child three times instead of two times as usual, this is referred to as „trisomy“. If one chromosome is missing from a pair of chromosomes and is thus present only once instead of twice as usual, this is known as „monosomy“. Depending on which chromosome is affected, the child’s mental and physical development can be very different. However, many chromosomal disorders prevent the occurrence of pregnancy or cause early miscarriages.
Did you know?
In principle, the PrenaTest® can examine the entire genetic material of your unborn child. The test options range from examining the most common chromosomal disorder, trisomy 21, to rare chromosomal disorders, which often only affect the placenta but can have a negative impact on the course of pregnancy.
Trisomy 21, 18 und 13
The most frequent is trisomy 21, in which chromosome 21 is present three times in the child instead of twice. It causes Down syndrome and occurs approximately once in every 500 to 800 births. The risk of maldistribution of chromosome 21 increases with increasing age of the woman and also of the man. Trisomy 18, also known as Edwards syndrome, occurs much more rarely. It occurs in approximately one out of 5000 newborns. Trisomy 13, known as Patau syndrome, is even rarer. Estimates indicate that it occurs once in every 16,000 births.
Maldistributions of the sex chromosomes
Girls/women usually have two X chromosomes (XX), boys/ men have one X and one Y chromosome (XY). If the sex chromosomes passed on by the parents are not correctly distributed when an embryo is created, an embryo with different chromosome numbers can result:
- Turner syndrome (X0): occurs approximately once in every 2,500 female newborns.
- Triple X syndrome (XXX): occurs approximately once in 1,000 female newborns
- Klinefelter syndrome (XXY): occurs approximately once in 500 male newborns
- Jacobs syndrome (XYY): occurs approximately once in 1,000 male newborns
Trisomies or monosomies of the other chromosomes
These chromosomal disorders usually have such serious consequences for the development of the embryo that an early miscarriage usually occurs, possibly so early that the onset of pregnancy was not noticed at all. However, if not all cells of the embryo or even only cell areas of the placenta are affected, this can have a negative impact on the course of pregnancy.
DiGeorge syndrome, microdeletion 22q11
This is neither a trisomy nor a monosomy. Instead, a small piece of chromosome 22 is missing. Such a disorder occurs in one of approximately 6,000 newborns. It can trigger malformations in the embryo, which may be noticed during ultrasound examinations. If there is any suspicion, the presence of such a microdeletion can be examined with the PrenaTest®.
The human chromosome set
The human chromosome set
The genetic material in all cells of the human body is organized in the form of chromosomes. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. The first 22 pairs are numbered consecutively and are known as „autosomes“ (chromosome 1 to chromosome 22). The last two chromosomes determine sex and are known as „gonosomes“ or sex chromosomes (X and Y). Girls have two X chromosomes and boys have one X and one Y chromosome. Cells multiply by dividing over and over. Before each cell division, the chromosomes double in order to be evenly divided among the two newly created cells.
What are chromosomal disorders and how do they arise?
Chromosomal disorders are changes to the chromosomes. They develop accidentally due to errors during the maturation of egg and sperm cells (germ cells) or – more rarely – due to errors during cell division during the development of the fertilized egg cell. When cells develop in which the number of chromosomes no longer add up, the cells are described as having numerical chromosome disorders or chromosome maldistribution. For example, a chromosome may be missing, that is, there are only 45 chromosomes in the cell, or there may be one chromosome too many in the cells, that is, the cell has 47 instead of 46 chromosomes.
Development of a chromosome disorder (trisomy)
Please have your doctor explain to you which level of safety the PrenaTest® can offer you and how.