The deep posterior vaginal vault is located in the posterior part of the annular depression between the upper end of the vagina and the cervix of the uterus, and is the clinical site for performing a vaginal vault puncture. The upper end of the vagina is wide and encircles the vaginal part of the cervix, forming an annular depression between the two, which is called the vaginal vault. The vaginal vault is divided into interconnected anterior, posterior and lateral parts, with the posterior vaginal vault being the deepest. Behind and above the posterior vaginal vault is the recto-uterine pit, separated only by the posterior vaginal wall and the peritoneum. The rectovaginal pit is the lowest part of the pelvis. When there is pelvic pus or bleeding from a ruptured ectopic pregnancy, a puncture can be made through this area to draw out the blood or fluid to help diagnose the condition, and to drain the blood and fluid from the rectovaginal pit to relieve the condition. When pelvic pain, fever or sudden abdominal pain during pregnancy occurs, you should go to the hospital in time to find out the cause of the disease. If pelvic pus or blood accumulation is suspected, posterior vaginal fornix puncture can be performed to aid in diagnosis and further treatment.