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.
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
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
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.
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.