Edward syndrome – the cause of chromosomal trisomy 18.
Edward Syndrome – Chromosome 18 trisomy is the second most common chromosomal aberration after Down syndrome.
Under normal circumstances, each somatic cell of the human body contains 46 chromosomes, 23 chromosomes from each parent.
In some cases, there may be a disturbance in the number of chromosomes, i.e. certain excess chromosomes may occur, which are manifested by various changes in organ function, intelligence, and phenotype.
About 5% of children develop mosaicism when some cells in the body have an excess of chromosome 18, while others have a normal number of chromosomes.
The severity of the disease depends on the type and number of cells that have an excess chromosome. The development of such persons can vary from normal to severe compromising.
Most babies born with Edwards syndrome are fragile and weak, with low birth weight. The head is extremely small. The ears are set and deformed low, and the mouth and lower jaw are small (micrognatia).
Babies with this syndrome may also have a cleft palate or lip.
The hands are usually held in fists with the second finger passing the third and the fifth passing the fourth (flexion contractions of the fingers).
Babies with Edward syndrome may have deformed feet as well as joined or intertwined toes. Children with this syndrome may have problems with the lungs, heart, kidneys, diaphragm, and blood vessels.
Edward syndrome – risk factors
In most cases, this deviation is not inherited but occurs as an accidental phenomenon during the formation of sperm or eggs (spermatogenesis, oogenesis).
During meiosis (cell division), chromosomes do not divide, so reproductive cells are formed with an abnormal number of chromosomes (instead of one, they contain two chromosomes 18).
When such a gamete is combined with a normal one during fertilization, an embryo with a chromosome 18 in excess is formed in all cells of the body.
Trisomy caused by a balanced displacement in one of the parents is inherited.
Such a parent contains a shift of chromosome 18 to another chromosome, and since there is no excess genetic material, the phenotype is normal, showing no signs of disease. Such persons have an increased risk of giving birth to children with trisomy 18.
What are all the tests for Edwards syndrome in pregnancy?
Combined examination in the first trimester (Double test) based on ultrasound measurements and biochemical tests determines the risk for Edwards syndrome, Down syndrome (trisomy 21), and Patau syndrome (trisomy 13).
The most reliable diagnostic methods are amniocentesis and choriocentesis. Amniocentesis (analysis of amniotic fluid, ie amniotic fluid) and choriocentesis (chorionic villus sampling) are tests that provide defined information.
However, these tests are invasive, and performing them increases the risk of miscarriage. For this reason, they are not proposed to all women.
Screening tests are tests that do not provide definitive information but determine the risk for Edvard syndrome and, most importantly, these tests pose no risk to either the fetus or the mother.
There are several types of screening tests, the most accurate of which is definitely the genetic screening test. If the screening test determines a high risk, the pregnant woman is referred to one of the invasive diagnostic tests.
Edvard syndrome – symptoms in pregnancy
During pregnancy, the mother has no symptoms that may indicate the existence of this syndrome in the baby. An ultrasound examination can determine with great certainty if there are any fetal abnormalities.
Ultrasound can show the structure of the heart, defects in the walls of the heart, as well as various abnormalities in the blood vessels. If there is a suspicion in the ultrasound examination, the expectant mother is referred for additional examinations.
Edward Syndrome – treatment?
There is no cure for Edwards syndrome, but the therapy is symptomatic and supportive.
About 65% of fetuses with chrysosome 18 trisomy do not live, i.e. abortion occurs. Only 50% of live births with this syndrome survive the first two months of life, and 5-10% survive the first year.
Learn more about the VERACITY prenatal test at AvicenaKS Laboratory.
VERACITY is a new generation test that accurately detects Down, Edvard and Patau syndromes, the three most common genetic disorders of the fetus, as well as other syndromes caused by aneuploidy of X and Y chromosomes.
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