Which category of chromosomal abnormality accounts for the largest proportion of first-trimester spontaneous miscarriages?
- A Monosomy X (45,X)
- B Autosomal trisomy ✓
- C Triploidy
- D Balanced reciprocal translocation
Correct answer: B. Autosomal trisomy
Explanation
About half of first-trimester abortuses are chromosomally abnormal, and autosomal trisomies form the largest group, with trisomy 16 being the single most frequent trisomy. Monosomy X is the most common individual karyotype in abortuses, which is why students confuse it with the answer, but trisomies taken together far outnumber it. Balanced rearrangements are usually compatible with normal development and rarely cause early loss.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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