This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urogynecology, Subject name: Gynaecology & Obstetrics
In Baden Walker Halfway system of classification of prolapse, the reference point is: 
Select and explain. 
A. Hymen, B. Introitus, C. Internal OS, D. External os
A: Hymen
Answer: A: Hymen 
Explanation: Baden walker halfway system STAGE DESCRIPTION 0 No descent of pelvis 1 leading edge of the prolapse remains 1cm or more above the hymenal ring II leading edge of the prolapse extends from 1 cm above to 1cm below the hymenal ring III From 1cm beyond the hymenal ring but without complete vaginal eversion IV Essentially complete eversion of vagina D.C.DUTTA&;S TEXTBOOK OF GYNAECOLOGY,Pg no:206,6th edition