Uterus prolapse is caused by a weakening of the muscle structures in the pelvis. Births and multiple births can cause the vagina to become relaxed as it weakens through added size.
When the internal structures in the pelvis are weak, they will no longer sustain the weight of internal organs and consequently, you can have a prolapse of an organ onto another organ. In this case, the uterus falls onto the vagina and it feels like your internal organs are falling out of you depending on the severity of the injury.
Severe prolapse of the uterus onto the vagina will make the vagina inaccessible during penetration and feel closed of where you cannot even insert a finger into the vagina without feeling discomfort or pain. On a more moderate side of this type of injury, you can see a dent in the vaginal canal where the uterus is pushing onto the vaginal wall.
With these types of injuries, it interferes with the ability to have sex in a normal manner, and in many cases, you simply cannot have intercourse as it can be painful and pure discomfort is felt, and like previously mentioned sometimes it's not possible for the insertion of anything into the vagina since its completely closed off. The use of pelvic restraints needs to be employed as a way to hold the organs from coming further down through the vagina.