<prompt> The shoest diameter of fetal head is :Biparietal diameterSuboccipito frontal diameterOccipito frontal diameterBitemoral diameter  <response>: Fetal head diameters Largest transverse diameter is biparietal diameter measuring approximately 9.5cms Shoest transverse diameter is bitemporal diameter measuring approximately 8cms Reference: Williams Obstetrics; 24th Edition; Chapter 5 The transverse diameters of fetal skull which are concerned with the mechanism of labor are -- Biparietal diameter--9.5 cm 3 34 : It extends between two parietal eminences. Whatever may be the position of the head, this diameter nearly always engages. -- Super-subparietal--8.5 cm 3 12 : It extends from a point placed below one parietal eminence to a point placed above the other parietal eminence of the opposite side. -- Bitemporal diameter--8 cm 3 14 : It is the distance between the anteroinferior ends of the coronal suture. -- Bimastoid diameter -- 7.5 cm 3: It is the distance between the tips of the mastoid processes. The diameter is incompressible and it is impossible to reduce the length of the bimastoid diameter by obstetrical operation. reference: D C Dutta Textbook of Obstetrics 7th edition page 85 