The shortest diameter of fetal head is:

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.