A couple has a child with Down syndrome due to standard trisomy 21 (47,XX,+21). The mother is 28 years old. Which statement about recurrence risk and prevention is correct?
- A The recurrence risk is determined by the mother's age at the time of the next conception ✓
- B The recurrence risk is approximately 1% for any future pregnancy, independent of maternal age
- C Preimplantation genetic testing cannot reduce recurrence risk in this couple
- D The recurrence risk is 25% because the condition follows an autosomal recessive pattern
Correct answer: A. The recurrence risk is determined by the mother's age at the time of the next conception
Explanation
For standard trisomy 21, the recurrence risk is the higher of approximately 1% or the age-specific risk for the mother's age at the next conception. Since the mother is 28, her age-specific risk is lower than 1%, so the recurrence risk is approximately 1% for this pregnancy, but it increases with advancing maternal age in future pregnancies. Preimplantation genetic testing can identify euploid embryos. Down syndrome is a chromosomal aneuploidy, not an autosomal recessive condition.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.