This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'All of the following are the most commonly used ultrasonographic fetal growth parameters for estimating gestational age of the fetus, EXCEPT: \nSelect and explain. \nA. Biparietal diameter, B. Head circumference, C. Transcerebellar diameter, D. Femur length', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Transcerebellar diameter and biorbital diameter are less commonly used measurements used for dating pregnancy between 14-20weeks of gestation. It is used paicularly when menstrual dates are unavailable. It becomes less accurate afterwards. Ref: Protocols for High-Risk Pregnancies By John T Queenan, 5th Edition, Page 425 ; Oxford Desk Reference : Obstetrics and Gynaecology By Sarabatnam Arulkumaran, Page 48 ; Diagnostic Imaging of Fetal Anomalies By David A. Nyberg, Page 32-4', 'role': 'assistant'}]