The Need for Genetic Diagnostics in Planning a Pregnancy
The term “genetics” , though used casually, becomes important when we are looking at planning a baby . For a couple planning a family, the main goal is to have a healthy child. While most gynecologist or primary health care providers would check for blood group compatibility, infections, thyroid functions, other hormone levels and blood sugar as a measure of the general health of the couple , often taking a family history along with such preconception testing helps in planning a pregnancy better.
India is a vast country with diverse and multiple castes, ethnic groups, religions, occupations, economic strata, languages, socio-cultural traditions, genetic heritages and life-styles and practices. Moreover, this country has absorbed in so many racial, religious, socio-cultural, linguistic and genetic elements that have given rise to amalgamation and conglomeration of all the constituent features, representing the cohesive unity in diversity in the true sense. The population of India is thus extremely diverse comprising of more than 3,000 ethnic groups who still follow endogamy.
Due to the high birth rate in India a very large number of infants with genetic disorders are born every year almost half a million with malformations and 21,000 with Down syndrome. In a multi-centric study reported by Verma et al (2000 and 2004) on the causes of referral for genetic counseling the top four disorders were repeated abortions (12.4%), identifiable syndromes (12.1%), chromosomal disorders (11.3%) and mental retardation (11%). In a more recent study ( Verma 2014) in a private hospital the top reasons for referral were reproductive genetics (38.9%)--comprising prenatal diagnosis, recurrent abortions, infertility and Torch infections--mental retardation +/- multiple congenital anomalies (16.1%), Down syndrome (9.1%), thalassemia/haemophilia (8.8%), and muscle dystrophy/spinal muscular atrophy (8.4%). A recent study carried out in three centers (Mumbai, Delhi and Baroda) on 94,610 newborns by using a uniform proforma showed a malformation frequency of 2.03%, the commonest malformations are neural tube defects and musculo-skeletal disorders. Screening of 112,269 newborns for aminoacid disorders showed four disorders to be the commonest--tyrosinemia, maple syrup urine disease and phenylketonuria. Screening of cases of mental retardation for aminoacid disorders revealed four to be the commonest--hyperglycinemia, homocystinuria, alkaptonuria, and maple syrup urine disease. Metabolic studies of cases of mental retardation in AIIMS, Delhi and KEM Hospital, Mumbai, demonstrated that common disorders were those of mucopolysaccharides, lysosomes, Wilson disease, glycogen storage disease and galactosemia. It is estimated that beta- thalassemia has a frequency at birth of 1:2700, which means that about 9,000 cases of thalassemia major are born every year. Almost 5200 infants with sickle cell disease are born every year. Disorders, which deserve to be screened in the newborn period, are hypothyroidism and G-6-PD deficiency, while screening for aminoacid and other metabolic disorders could presently be restricted to symptomatic infants (Verma, 2001).
From the above discussion it can be summarized that the impact of genetics in medicine is indispensible. This is because most clinical manifestations have a genetic component associated with it viz
- 3-4 % of all births are associated with major congenital malformations
- 1in 13 conception has chromosomal abnormality
- 50 % of all first trimester abortions have gross chromosomal abnormality or micro deletions
- 0.2 % babies are born with chromosomal rearrangements
- 5.6 and 11.5 % still births and neonatal deaths respectively are associated with a genetic cause
- Mental retardations can often be linked to have a significant genetic component
- Presence of community genetic issues like Thalasemia which are more prevalent in these parts of the world.
- Infants with Metabolic disorders
- Infants with Neural tube defects
Additionally, Couple who have consanguinity, or a affected brother or sister or first cousin or even maternal aunts or uncles who might have certain conditions like neuro-motor problem, intellectual disabilities, hearing loss since birth, unable to speak since birth , neonatal deaths in family, h/o of seizure disorders / epilepsy can be referred for a genetic clinic. Additionally, few regions have high incidence of certain disorders like Thlalassemia, Sickle cell Anemia etc.
It becomes very important to screen such patients as the genetic background in such disease manifestations helps to delineate the management of the disease.
Depending upon the need of the medical problem, a genetic screening test can be:
Screening test: Depending on the disease incidence in a region, few diseases or syndromes can be screened even before the symptoms appear in the infant without any indications or family h/o. This is done, as many cases actionable management can be and early intervention can prevent harm or crisis in the child. Normally such tests are cheap and requires additional confirmation by further testing if screened positive. Like the New born screening test panel.
Diagnostic testing : This means that the primary care provider has established a certain medical condition and would need confirmation on his finding.
Carrier testing: The primary care provider and the genetic counselor identifies that the potential person might be at risk because of medical presentation in his or his partners family. So targeted testing would be conducted to establish the genetic background of the person for him /her to plan their future
Predictive testing: The person is in a particular high risk area or age group or from a community which has a high disease incidence of a particular disease or wants to understand his own genetic background with respect to some familial genetic problems in distant relatives.
The primary care provider needs to be aware of the possibilities and if a medical problem arises or is presumed to arrive, he/ she refers the family to a genetic counselor for genetic evaluation and screening. A genetic counselor deals with problems associated with the manifestations of a particular genetic diseases or helps in accessing the recurrence risks of genetic disorders in families and orders genetic screening if required. This involved
- Talking to families and gathering detailed information on family medical histories in order to create pedigree charts that help in better evaluation of the disease occurrence or recurrence risk.
- Once such analysis is done the counselor would enlighten the families in simple language about the inheritance pattern, disease screening, management, prevention and inform the family about the recent research advancement if any in that field.
- The counselor would estimate the possible risks and discuss all avenues in a nondirective and unbiased way and help the family in making an informed decision.
Early intervention in many cases have been established to have better outcomes than when the disease is established at a later stage or if left without proper intervention. In cases of many metabolic disorders the window for intervention is the first few months, after which if detected, the intervention is not as effective. A confirmed genetic testing helps the clinician to explain the diagnosis to the family setting their expectations from the child and healthcare provider and also helps proper surveillance of the disease. Knowing the genetic diagnosis can help the primary pediatrician plan the care and hence manage the disease better. Further it often gives closure to the family and helps them cope with the situation at hand. Also, the family is able to further plan subsequent pregnancies, where prenatal testing can help reduce the disease burden.
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