<prompt> The diameter of fetal head, which comes in totally deflexed head :Suboccipito-frontalOccipito-frontalSubmento-bregmaticSuboccipito-bregmatic  <response>: Circumferences of the head in different attitudes: -- Complete flexion Biparietal-suboccipito-bregmatic. Shape -- almost round 27.5 cm 11 -- Deflexed Biparietal-occipito-frontal. Shape -- oval 34 cm 13 12 -- Incomplete extension Biparietal-mento-veical. Shape -- bigger oval 37.5 cm 15 -- Complete extension Biparietal-submento-bregmatic. Shape -- almost round 27.5 cm 11 Reference: D C Dutta Textbook of Obstetrics 7th edition,page 85. 