A routine 20-week anomaly scan shows two fluid-filled structures in the upper abdomen of the fetus, one being the stomach and the other a dilated proximal duodenum, communicating across the pylorus. Which chromosomal abnormality is most classically associated with this finding?
- A Trisomy 21 ✓
- B Trisomy 18
- C Trisomy 13
- D 45,XO
Correct answer: A. Trisomy 21
Explanation
The double bubble sign of stomach plus dilated duodenal cap is the sonographic picture of duodenal atresia, and roughly 30 to 40 percent of fetuses with this lesion have trisomy 21. Trisomy 18 is linked to clenched fists and rocker-bottom feet, trisomy 13 to holoprosencephaly and cyclopia, and 45,XO to cystic hygroma and hydrops, so these are the distractors that fail.
Reference: Callen's Ultrasonography in Obstetrics and Gynecology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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