This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'The following are related to face presentation except: \nSelect and explain. \nA. The commonest position is LMA, B. Engaging diameter is submentobregmatic, C. The diameter distending the vulval outlet is mentovertical, D. During moulding, there is elongation of occipitofrontal diameter', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Face presentation:\n\nThe attitude of the fetus shows complete flexion of the limbs with extension of the spine. There is complete extension of the head so that the occiput is in contact with the back.\nThe denominator is mentum.\nThe commonest position is left mentoanterior (LMA).\nFace presentation present during pregnancy (primary) is rare, while that developing after the onset of labor (secondary) is common. It occurs more frequently seen in multiparae (70%), like other malpresentations.\nMost common maternal cause is platypelloid pelvis and most common fetal cause is anencephaly.\nThe diameter of engagement is the oblique diameter—right in LMA, left in RMA.\nThe engaging diameter of the head is submento-bregmatic 9.5 cm (3 3/4”) in fully extended head or submentovertical\xa0 11.5 cm (4 1/2”) in partially extended head.\nEngagement is delayed because of long distance between the mentum and biparietal plane (7 cm).\nThe head is born by flexion: (11.5 cm).\nVaginal delivery is possible in nentoanterior positions but not in persistent mentoposterior.\nIn mentoposterior during early stages of labor the policy of wait and watch should be adopted, in hope of mentoposterior getting converted to mentoanterior spontanelously. Persistent mentoposterior position is an indication for doing cesarean section.', 'role': 'assistant'}]