SN4 SHORT NOTE 5M

Write a short note on genetic counselling — principles, indications, steps and ethical issues.

General Medicine · Final Professional

Definition

Genetic counselling is the communication process by which individuals or families at risk of a genetic disorder are helped to understand the medical facts, the mode of inheritance, the risk of recurrence, and the options available, and are supported in making decisions that are their own and acting in accordance with them. It is fundamentally non-directive: the counsellor informs and supports but does not decide.

Indications

Previous child, or family history, of a genetic or congenital disorder.
Advanced maternal age (≥ 35 years) or advanced paternal age.
Consanguineous marriage — highly relevant in India, where it raises the risk of autosomal recessive disease.
Recurrent pregnancy loss, stillbirth or neonatal death.
Known carrier state — thalassaemia, sickle cell disease, haemophilia, Duchenne muscular dystrophy.
Abnormal antenatal screening or ultrasound finding.
Exposure to a teratogen (drugs, radiation, infection) in pregnancy.
Family history of an adult-onset genetic disorder — Huntington's disease, hereditary breast/ovarian cancer (BRCA1/2), familial hypercholesterolaemia.

Steps in Genetic Counselling

1. Establish the diagnosis precisely — everything downstream depends on it. Use clinical examination, karyotyping, FISH, chromosomal microarray, and targeted or next-generation sequencing.

2. Construct a three-generation pedigree, recording consanguinity, miscarriages, deaths and affected relatives.

3. Determine the mode of inheritance — autosomal dominant, autosomal recessive, X-linked, mitochondrial or multifactorial.

4. Estimate recurrence risk — Mendelian risk for single-gene disorders; empiric risk for multifactorial conditions; Bayesian modification where carrier testing is available.

5. Communicate in simple, non-technical language, without pressure, allowing several sessions.

6. Discuss options: prenatal diagnosis, preimplantation genetic diagnosis, gamete donation, adoption, contraception, or accepting the risk.

7. Provide written summary and long-term follow-up, with referral for psychological support.

Inheritance Pattern	Recurrence Risk	Examples
Autosomal dominant	50% to each offspring	Marfan syndrome, Huntington's disease, NF-1
Autosomal recessive	25% if both parents carriers	Thalassaemia, sickle cell disease, cystic fibrosis
X-linked recessive	50% of sons affected, 50% of daughters carriers	Haemophilia A & B, Duchenne muscular dystrophy
Mitochondrial	All children of an affected mother	MELAS, Leber's hereditary optic neuropathy
Multifactorial	2–5% empiric	Neural tube defects, cleft lip/palate, diabetes

Prenatal Diagnostic Methods

Chorionic villus sampling at 10–13 weeks — earliest, small risk of miscarriage.
Amniocentesis at 15–18 weeks — the standard method.
Cordocentesis after 18 weeks.
Non-invasive prenatal testing (NIPT) using cell-free fetal DNA in maternal blood — a screening test for aneuploidy, requiring confirmation by an invasive test.
Ultrasound for structural anomalies; preimplantation genetic diagnosis with IVF.

EXAM TIP

In India, prenatal testing for sex determination is a criminal offence under the PCPNDT Act, 1994. Prenatal diagnosis may be offered only for genetic disease, and the sex of the fetus must never be disclosed. Mention this Act — examiners look for it.

Ethical Principles

Autonomy (the couple decides), confidentiality (results not disclosed to relatives or employers without consent), non-directiveness, informed consent, right not to know (especially for untreatable adult-onset disease such as Huntington's), and avoidance of eugenic pressure. Testing of asymptomatic children for adult-onset disorders is generally deferred until they can consent.

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