This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Gynae), Subject name: Gynaecology & Obstetrics
Vaginal delivery is not possible in which of the following positions of fetus? 
Select and explain. 
A. Right occipitoposterior position, B. Occipitotransverse position, C. Mentoposterior position, D. Breech with extended legs
C: Mentoposterior position
Answer: C: Mentoposterior position 
Explanation: Ans. c (Mentoposterior position). (Ref. Textbook of Obstetrics by Dutta, 4th ed., 396, 409, 420)OCCIPITOPOSTERIOR:-# 1st stage: In uncomplicated cases labour conducted in usual manner, however special instructions as for occipito- posterior position is to be followed and hoping for spontaneous anterior rotation of chin.# 2nd stage: If anterior rotation of chin occurs spontaneously - then use forceps for further delivery.# But if incomplete or malrotation persists -LSCS will be ideal, however manual rotation may be tried.# However occipitoposterior per se is not an indication for LSCS.# Pelvic inadequacy, unfavourable configuration of pelvis and fetal anomaly usually need LSCS.