The shoest diameter of fetal head is :
Fetal head diameters Largest transverse diameter is biparietal diameter measuring approximately 9.5cms Shoest transverse diameter is bitemporal diameter measuring approximately 8cms Reference: William's 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 3/4 ''): 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 1/2 ''): 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 1/4 ''): 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
Biparietal diameter
Suboccipito frontal diameter
Occipito frontal diameter
Bitemoral diameter
General obstetrics