Purpose and principles
Deliver non-directive genomic counselling, calculate and communicate recurrence risk from diagnosis and inheritance, explain uncertainty and reproductive options, support family communication and document an agreed plan across life stages.
Genetic counselling helps a person or family understand a diagnosis, adapt to its implications and make decisions consistent with their own values. A good consultation is reciprocal. Ask what prompted the appointment, what the family already believes, whether there is guilt or blame, who should be present and what outcome would be useful today. Use a professional interpreter rather than a child or relative when language support is required. Explain specialist terms in ordinary words, invite teach-back and accept that several conversations may be needed before reproductive decisions.
Risk calculation starts with evidence quality. Review the original laboratory report, clinical criteria, phenotype and three-generation pedigree. Confirm whether a variant is pathogenic, likely pathogenic or uncertain; whether disease is autosomal dominant, recessive, X-linked, mitochondrial, chromosomal or multifactorial; whether parental samples establish de novo status; and whether penetrance or sex limitation applies. Do not quote a familiar fraction when the familial diagnosis is unverified. A one-in-two transmission chance for an autosomal dominant variant may coexist with a lower or age-dependent disease chance.
Autosomal recessive counselling distinguishes an affected person, a carrier and population carrier probability. Two confirmed carriers of pathogenic variants in the same gene usually face a one-in-four chance of an affected child, one-in-two chance of a carrier and one-in-four chance of a child inheriting neither familial variant in each pregnancy. If variants have different severity, reduced penetrance or uncertain phase, specialist interpretation modifies that simple model. Testing a partner begins with ancestry-independent clinical criteria and the familial mechanism, not with assumptions based on ethnicity alone.