A healthy 24-year-old woman is found on karyotype to carry a balanced Robertsonian translocation involving chromosome 21: 45,XX,der(14;21)(q10;q10). Her husband has a normal karyotype. What is the approximate recurrence risk of Down syndrome in her offspring?
- A Less than 1 percent
- B About 10 to 15 percent ✓
- C About 5 percent
- D About 50 percent
Correct answer: B. About 10 to 15 percent
Explanation
For a female carrier of a balanced 14;21 Robertsonian translocation, empirical recurrence risk for trisomy 21 offspring is approximately 10 to 15 percent per pregnancy. If the father were the carrier instead, the risk drops to about 1 to 3 percent, likely reflecting selection against abnormal sperm. A risk below 1 percent applies to de novo translocations, while 50 percent would apply only if segregation always produced a translocation trisomy, which it does not.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.