Screening (for Genetic and Other Disorders) of Embryos and Newborns: Why it is important?

A healthy baby is all expecting parents' desire. With new advancements in medical technology, it is now possible to detect metabolic diseases in newborn baby and locate genetic disorders in embryos, thus making it possible to detect genetic and other disorders at an early stage.

Metabolic and genetic disorders can hinder the normal growth and mental development of the baby in many possible ways. 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. Researchers suggest the importance of genetic screening that screens the embryo for all the genetic disorders it may have acquired or developed as a result of some chromosomal mutation and thus can be treated accordingly. This is possible through a medical process called Pre-Implantation Genetic Diagnosis.

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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