This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Prenatal Diagnosis, Subject name: Gynaecology & Obstetrics
[{'content': 'The Parameter measured in the USG, measures 3.7 mm. It is: \nSelect and explain. \nA. Normal finding, B. Higher than normal, C. Lesser than normal, D. The scan should be repeated at 18 weeks', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Nuchal translucency (NT) is the sonographic appearance of a collection of fluid under the skin behind the fetal neck in the first-trimester of pregnancy. In fetuses with chromosomal abnormalities, cardiac defects and many genetic syndromes -NT thickness is increased. Up to 3 mm is considered normal. More than 3 mm NT is one of the markers of Down syndrome on USG.', 'role': 'assistant'}]