Chromosomal diseases can be totally prevented by prenatal testing. Prenatal testing or genetic testing can provide information regarding the genetic makeup of the unborn child. Read on to know more about prenatal testing for chromosomal diseases.
Chromosomal diseases have terrific potential to render an adverse impact on the lives of the affected individuals and their families. They make the living of normal life near to impossible and therefore it is extremely essential that every attempt must be made to test the possibility of chromosomal diseases. Through prenatal
testing it is possible to derive information regarding their possibility in the unborn child and whether the chromosomal disorder will be passed on from the carrier to their offspring.
Why is Prenatal Testing for Chromosomal Diseases so Important?
Amongst half of all the abortions occurring within the first trimester of a pregnancy, chromosomal disorder is responsible. The condition is medically termed as conceptus, where about 8% or one in thirteen chromosomes is abnormal. It has also been found that 6 to 11% of the still births and neonatal deaths that occur are caused by chromosomal disorder. Amongst the affected fetuses who manage a life in this world, are actually born with a major congenital defect; this accounts for 34%. By the time the babies are 7-8 years, about 4% amongst them are discovered with a chromosomal defect. Therefore in order to ascertain the normal and healthy life of the unborn baby it is always desirable to chromosomal disease screening during the prenatal tests.
Here is Why the Testing is Important and What the Diseases Mean
As said earlier even in live birth, chromosomal abnormality is possible. If the mother happens to be in the late years of her reproductive age, she develops a condition called maternal meiotic non disjunction. This is likely to result in autosomal trisomies, a chromosomal disease. Then there is a possibility of numerical sex chromosome abnormality which is a follow through of either non-disjunction from either the maternal or paternal side.
Trisomy is another condition attributed to maternal meiosis I. Although this is not directly related to the age of the mother but is has been observed that with an advanced age the fetal aneuploidy enhances along with the possibility of meiotic errors. This is why along with the prenatal testing for chromosomal abnormalities; doctors suggest karyotype analysis and/or genetic amniocentesis as a part of regular screening.
Sex Chromosome Abnormality
is another variant that is found to occur once is every 300-500 births. The condition is attributed to a chromosome error like 45, X; 47, XXY; 47, XXX; 47, XYY and is broadly known as mosaicism. This means that two or more cell populations of the individual have different karyotype. The root of this chromosome error can be both maternal and paternal and if the woman has a previous history of fetal XXX or XXY, prenatal testing is a must. A recurrent risk of another fetal trisomy can be effectively adjudged then.
Translocations and inversions are another type of chromosomal disorder. The reciprocal exchange of genetic material between two varieties of chromosomes that are nonhomologous is called translocation. In this process the arm of each chromosome breaks and the genetic material at the breakpoint gets exchanged. If the translocation is balanced no genetic material is lost or gained. But conditions characterized by infertility, early pregnancy loss happen when unbalanced gametes are formed even by a carrier of balanced translocation. A prenatal chromosomal testing can determine whether the fetus will develop as an aneuploid child due to this condition.
When the same chromosome breaks into two, inversions are caused. The segment between the break points gets inverted even before they get naturally repaired. This does not result in loss of genetic material but the gene sequence gets altered. This results in a potential chromosomal abnormality.