Parents also fear the transmission of genetic disorders in their children.
Genetic screening is often recommended to parents with genetic diseases.
However, there may be parents who are carriers of a genetic disease and may not
necessary be the victims. In such cases, there are 50% chances that the embryo
will be a carrier and not the victim.
Pre-Implantation
Genetic Diagnosis (PGD) also referred to as Embryo Screening is performed on
embryos prior to implantation. It is an
In
vitro Fertilization (IVF) technique that screens the embryos for any
alleles that are responsible for any genetic disease. With this method parents
get to know if the embryo has any genetic disorder and thus allow them to
decide on how they would like to proceed with the pregnancy.
Pre-implantation genetics is used
exclusively for major and small groups of genetic abnormalities like Duchenne
muscular dystrophy, cystic fibrosis etc. Embryo screening involves
artificially combining sperm cells with many egg cells so as to create many
embryos. The DNA of these embryos are then analyzed for any defective genes and
identified. Embryo screening reduces the chances of baby being affected with
any chromosomal abnormality or genetic disorder. The tests are performed for
different diseases including aneuploidy, single gene disorders and chromosomal
mutations.
Unlike Pre-Implantation Genetic screening which screens embryos,
New Born screening identifies metabolic disorders in infants. New
Born Screening is the practice of testing the blood sample or body tissue of
the new born for metabolic disorders. The blood is collected from the heels of
the infant and is tested on third day when the maternal thyroid stimulating
hormone has subsided in the blood. The blood is sent to the laboratory where it
is screened for various diseases. If the test result is positive, the child is
referred to specialists for further treatment.
A priority list of disorders that are
screened in all newborns comprises of congenital hypothyroidism,
hyperphenylalaninaemia, galactosaemia and maple syrup urine disease. These
disorders interfere with the infant's ability to absorb nutrients from the body
for normal growth and production of energy and thus should be detected early
and treated accordingly. If these disorders are left undiagnosed they may lead
to retarded growth, weakness, weight loss and may ultimately lead to death.
Researchers have observed that infants with
severe immunodeficiency diseases appear normal at the birth and usually have no
family history of immunodeficiency diseases. These diseases remain undiagnosed
until life threatening infection starts occurring.
However, if the infants are screened, these diseases can be diagnosed early and
can be improved with proper treatment before the onset of any serious symptoms
or infections. It is also believed that the administration of certain vaccines
to new born may aggravate the disease like T-cell lymphopenia and may cause
serious infection.
New
Born screening also diagnose diseases related to the endocrine gland that is
otherwise difficult to cure if diagnosed later. Early diagnosis allows better
treatment saving the baby from lifelong impairment. Thus, with the help of
screening it is possible to save the baby from serious diseases like Sickle
cell disease, congenital deafness; hyperplasia etc.
Reference : The clinical aspects of newborn screening:
importance of newborn screening follow-up. James PM, Levy HL
Source: Medindia
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