# POP-Q Staging of Prolapse > POP-Q staging of prolapse with reference points Aa to Bp, total vaginal length and stages 0 to IV, worked through for NEET-PG OBG exam preparation. - Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/pop-q-staging-of-prolapse - Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Shaw's Textbook of Gynaecology; Dutta's Textbook of Gynecology; Williams Gynecology - How to cite: "POP-Q Staging of Prolapse", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/pop-q-staging-of-prolapse ## Direct answer POP-Q staging of prolapse is the standardised pelvic organ prolapse quantification system, recording nine measurements in centimetres relative to the hymen, which is set at zero, and placing prolapse in stage 0 to stage IV. The stage is decided by the leading point, the most distal of Aa, Ba, Ap, Bp, C and D: stage II means within 1 cm of the hymen, stage III means more than 1 cm below it but short of total vaginal length minus 2 cm, and stage IV means eversion beyond that threshold. ## What you must remember - **Aa and Ap:** points 3 cm proximal to the hymen on the anterior and posterior vaginal walls, the fixed reference points that normally measure minus 3. - **Ba and Bp:** the most distal points of the anterior and posterior walls, the usual leading points in cystocoele and rectocoele staging. - **C and D:** the cervix or vault scar point and the posterior fornix, with D not recorded after hysterectomy. - **Genital hiatus, perineal body and TVL:** the hiatus is measured from the middle of the external urethral meatus to the posterior midline hymen, the perineal body from there to the middle of the anal opening, and total vaginal length with the prolapse reduced. - **Stage 0:** no prolapse, with Aa, Ba, Ap and Bp all at minus 3 cm and C or D no higher than minus (TVL minus 2) cm. - **Stage I:** the leading point is more than 1 cm above the hymen (higher than minus 1 cm) but the criteria for stage 0 are not met. - **Stage II:** the leading point lies between 1 cm above and 1 cm below the hymen, the commonest source of error in examination questions. - **Stage III and IV:** stage III lies more than 1 cm below the hymen but short of TVL minus 2 cm, while stage IV is eversion to or beyond that point. ## Worked example: staging a leading anterior point A 58-year-old woman has a total vaginal length of 8 cm with the prolapse reduced. On straining, her measurements are Aa at minus 1 cm, Ba at plus 2 cm, C at minus 2 cm, Ap at minus 2 cm and Bp at minus 3 cm. 1. **Find the leading point.** The leading point is the most distal measurement, and Ba, at plus 2 cm, is the most distal point, so it determines the stage. 2. **Compare with the hymen.** Plus 2 cm is more than 1 cm below the hymen, so the prolapse is at least stage III. 3. **Check the stage IV threshold.** Total vaginal length minus 2 cm gives 6 cm here, and plus 2 cm is well short of it, so the prolapse is stage III rather than stage IV. 4. **Report each compartment.** Each compartment is then reported separately, with its own leading point. Working through the arithmetic in this order, identifying the leading point and then the two thresholds, is the method examiners reward. ## Traps in the staging arithmetic Staging questions are usually a numerical puzzle, and most errors come from the hymen boundary and the sign convention. - **Trap:** placing stage II at the introitus or anywhere inside the vagina. — **Correct:** stage II is strictly within 1 cm either side of the hymen, which is the commonest confusion in staging questions. - **Trap:** reading a negative point as a more severe stage. — **Correct:** points above the hymen are negative, so a leading point at minus 2 cm is stage I, not a more severe stage. - **Trap:** forgetting that D is absent after hysterectomy and that TVL sets the stage IV threshold. — **Correct:** point D is not recorded after hysterectomy, and total vaginal length is needed for the stage IV threshold. Naming the leading point, the hymen reference and the TVL threshold in that order removes most of these errors. ## Frequently asked questions ### Which point defines stage II prolapse on POP-Q? Stage II prolapse is defined by the leading point lying within 1 cm above or below the hymen. This makes the hymen the reference plane for staging, and the leading point, not the average, decides the stage. ### What is total vaginal length used for in POP-Q staging? Total vaginal length, measured with the prolapse reduced, sets the threshold for stage IV, which is reached when the leading point is beyond total vaginal length minus 2 cm. It is therefore needed to distinguish stage III from stage IV. ### Why is Ba the commonest leading point in POP-Q staging? Ba is the most distal point of the anterior vaginal wall, and anterior compartment prolapse, or cystocoele, is the commonest form of vaginal descent. The leading point is therefore most often Ba in examination questions on prolapse. ### Which POP-Q measurement is not recorded after hysterectomy? Point D, the posterior fornix, is not recorded after hysterectomy because there is no fornix to measure. The cuff scar is then recorded at the C position, and the remaining points are measured as usual.