This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics of Common Disorders, Subject name: Pediatrics
[{'content': 'First trimester USG finding in Down syndrome- \nSelect and explain. \nA. Nuchal thickening, B. Nuchal translucency, C. Cardiac anomalies, D. GI anomalies', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Nuchal translucency Maternal serum screeningo 1st trimesterMaternal beta hCGo Higher than chromosomal ly normal fetuseso Difference increases with gestationPAPP-Ao Lower than chromosomally normal fetuseso Difference decreases with gestation: therefore not commonly used as a second-trimester testo 2nd trimesterTriple screeningMaternal free beta hCG: higher than chromosomally normal fetusesAFP: lower than chromosomally normal fetusesUnconjugated oestriol (uE3): lower than chromosomally normal fetusesUltrasoundo First trimesterNuchal translucency: thickness depends on the size of the fetus (CRL), but in general it is considered abnormal if >3 mm.There is recent evidence thai the inclusion of nasal bone measurement improves the specificity of 1st trimester datao Second trimesterApproximately 30% of babies with Down syndrome have detectable abnormalities on the mid-trimester ultrasound 1.", 'role': 'assistant'}]