Most common chromosomal abnormalities
The human body is an amazing machine. It consists of many cells; some sources indicate that there are more than 10 trillion of them! For our body to function properly, all of its components down to the smallest ones, such as DNA, must function properly. Despite its extraordinarily small size, DNA determines the characteristics of each individual. Our genetic record is stored in 23 pairs of chromosomes. At conception, each parent contributes 23 chromosomes or half of the child’s genetic material. These chromosomes are so important that any errors in our genetic code can have a profound effect on embryonic development.
Due to a random error in cell division, one of the parental sex cells may contain 1 chromosome too many, leading to a triple number of chromosomes or trisomy. They have different consequences, but all have a serious impact on the child’s development and health. Trisomies most common at birth are trisomy 21, 18, and 13. The cause of the tripled chromosomes is not yet known, but the consequences of additional chromosomes are well-defined.
Trisomy 21 – Down syndrome
The most common chromosomal abnormality in infants is trisomy of chromosome 21, known as Down syndrome. The risk of the presence of this syndrome increases with the mother’s age. This risk is 1 in 1000 at age 30, while at the age of 35, this risk rises increases to 1 in 400. Unfortunately, 30% of pregnancies with Down syndrome end in miscarriage.
Children with Down syndrome usually have mild to moderate mental development disorders. Early intervention and proper therapy are crucial for ensuring that their life is as normal and independent aa possible. Down syndrome is identified by characteristic facial features, decreased muscle tone (hypotonia), vertical eye folds, common heart diseases, and many other disorders. Only 1% of Down syndrome cases are hereditary.
The consequences of trisomy 21 are mild compared to other trisomies, as people with a mild form of the syndrome can live a relatively normal life.
You can read more about Down syndrome -> HERE
Trisomy 18 – Edwards syndrome
An additional chromosome 18 occurs in about one in 2,500 pregnancies and is three times more common in girls. Edwards syndrome is not usually compatible with life as 80% of such pregnancies end in miscarriage. Less than 10% of babies survive the first year of life.
Abnormalities resulting from Edwards syndrome are visible with ultrasound during pregnancy. At birth, babies exhibit low weight, small jaw, small ears, underdeveloped fingers, and more. Soon, they begin showing mental retardation.
Many children with Edwards syndrome have congenital heart disease and kidney problems. Genetic research shows that most trisomies of chromosome 18 are not heritable.
Trisomy 13 – Patau syndrome
Patau syndrome occurs in about 1 in 5,000 pregnancies. Unfortunately, 97% of such pregnancies end early with miscarriage. However, the vast majority of babies born do not live more than four months. Trisomy 13 is, in most cases, not hereditary.
Patau syndrome often causes abnormal functioning of the heart and brain, back problems, seizures, mental disability, and problems with other organs. At birth, we can spot a cleft lip or palate, undeveloped eyes, clenched fist, extra fingers, and other anomalies.
Each woman can have a child with chromosomal abnormalities. But with age, the risk of some of these abnormalities increases. All women, especially those aged 35 or more, are recommended to perform a prenatal non-invasive test such as NIPT by GenePlanet. As early as week 10, there is enough fetal DNA in the pregnant woman’s blood to enable the detection of potential genetic defects. A safe and simple test, NIPT by GenePlanet tests them with 99% sensitivity.