This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal Skull and Maternal Pelvis, Subject name: Gynaecology & Obstetrics
[{'content': 'The shortest diameter of fetal head is: \nSelect and explain. \nA. Biparietal diameter, B. Suboccipitofrontal diameter, C. Occipitofrontal diameter, D. Bitemporal diameter', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is d, i.e. Bitemporal diameterRef. Dutta Obs. 9/e. p 11MnemonicRemember Friends: always transverse diameters of the fetal skull are smaller than Anteroposterior diameters.Amongst the given options: Biparietal and bitemporal diameters are transverse diameters, whereas suboccipitofrontal and occipitofrontal are anteroposterior diameters.Now, the choice is between bitemporal and biparietal diameters.For memorizing this: learn a mnemonic, where transverse diameter are arranged in ascending order of their size.Miss = Bimastoid diameter = 7.5 cmTina = Bitemporal diameter = 8 cmS = Super subparietal diameter = 8.5 cmPretty = Biparietal diameter = 9.5 cmSo, our answer is bitemporal diameter (8 cm)Remember:In AP diameters:The longest AP diameter of fetal skull is mentovertical diameter = 14 cmThe second longest AP diameter is submentovertical = Occipitofrontal = 11.5 cm.', 'role': 'assistant'}]