Genetic counseling principles

Genetic counseling principles

Genetic counseling principles

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Indications - Who Gets a Consult?

  • Advanced Maternal Age (AMA): Age ≥35 at estimated date of delivery.
  • Abnormal Screening Results: Positive findings on aneuploidy screens (e.g., cfDNA, quad screen) or ultrasound markers (e.g., ↑ nuchal translucency).
  • Family History: Personal or family hx of a known genetic disorder, birth defect, or intellectual disability.
  • Previous Affected Pregnancy: History of a prior child with a chromosomal or genetic condition.
  • Teratogen Exposure: Significant exposure to medications, radiation, or infections linked to birth defects.
  • Consanguinity: Parents are related by blood.

High-Yield: Advanced Maternal Age (AMA) is the most frequent referral indication, driven by the age-related ↑ risk for fetal aneuploidies like Down syndrome.

Counseling Core - The Guiding Rules

  • Patient-Centered Approach: Focus on patient values, beliefs, and goals.
  • Non-Directive Counseling: Empower patients to make informed decisions that align with their own values. The counselor facilitates, but does not direct, patient choices.
  • Informed Consent: A critical process, not just a form. Ensures patient understands the risks, benefits, limitations, and alternatives of genetic testing.
  • Confidentiality: Uphold strict patient privacy regarding sensitive genetic information.
  • Psychosocial Support: Address emotional responses (e.g., anxiety, guilt) and family dynamics.

High-Yield Fact: The primary role of a genetic counselor is to provide information and support, not to recommend a specific course of action. Recommending termination or continuation of a pregnancy is inappropriate.

Testing Toolkit - Screen vs. Diagnose

  • Screening Tests: Assess Risk

    • Non-invasive or minimally invasive methods to identify pregnancies at ↑ risk for aneuploidy.
    • They do not diagnose; they provide a risk probability (e.g., 1 in 1,000).
    • Examples:
      • Cell-free DNA (cfDNA): Highest detection rate for common trisomies.
      • First Trimester Combined Screen: PAPP-A, β-hCG, nuchal translucency (NT).
      • Quad Screen: AFP, estriol, β-hCG, inhibin A.
  • Diagnostic Tests: Confirm Diagnosis

    • Invasive procedures offering a definitive yes/no answer.
    • Carry a small risk of pregnancy loss (~1 in 300-500).
    • Indicated after a positive screening test or for high-risk patients.
    • Examples:
      • Chorionic Villus Sampling (CVS): 10-13 weeks.
      • Amniocentesis: After 15 weeks.

⭐ A positive screening test result does not diagnose a fetal condition. It indicates that the risk is high enough to warrant offering definitive diagnostic testing (CVS or amniocentesis) for confirmation.

The Results Reveal - Now What?

  • Positive Screen: Not a diagnosis. Indicates ↑ risk, prompting the offer of definitive diagnostic tests.
  • Negative Screen: Low probability of the condition. Reassurance is provided; typically, no further aneuploidy testing is needed.
  • Counseling is Key: Discuss the positive predictive value (PPV), limitations of screening, and options for diagnostic testing (including risks/benefits). Patient autonomy is paramount.

Timing is critical for diagnostic choice: Chorionic Villus Sampling (CVS) is performed at 10-13 weeks, allowing for earlier diagnosis. Amniocentesis is performed later, typically after 15 weeks gestation.

High‑Yield Points - ⚡ Biggest Takeaways

  • The cornerstone is non-directive counseling; provide information and options, but the patient makes the final decision.
  • Always obtain informed consent before any genetic testing, respecting patient autonomy.
  • Key indications: advanced maternal age (AMA >35), abnormal screening, and positive family history.
  • Clearly distinguish between screening tests (assess risk) and diagnostic tests (e.g., amniocentesis, CVS) which are definitive.
  • Address patient emotions and maintain strict confidentiality.

Practice Questions: Genetic counseling principles

Test your understanding with these related questions

A 28-year-old woman comes to the physician for genetic counseling prior to conception. For the past year, she has had intermittent episodes of headache, nausea, abdominal pain, and tingling of her fingers. She also complains of dark urine during the episodes. Her mother and maternal uncle have similar symptoms and her father is healthy. Her husband is healthy and there is no history of serious illness in his family. Serum studies show elevated concentrations of porphobilinogen and δ-aminolevulinic acid. What is the probability of this patient having a child with the same disease as her?

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Flashcards: Genetic counseling principles

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Culture of the mother's vagina at _____ of pregnancy (time)is done to ensure Streptococcus agalactiae (GBS) has not colonized

TAP TO REVEAL ANSWER

Culture of the mother's vagina at _____ of pregnancy (time)is done to ensure Streptococcus agalactiae (GBS) has not colonized

35 wks

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