Many women with a mild prolapse go on to have healthy pregnancies, so a diagnosis is not a reason to rule one out. It is a reason to plan.
Pregnancy and delivery both put extra load on the pelvic floor, and what was a mild descent can feel different afterwards. Knowing how much support has been lost before you conceive means you and your doctors are comparing against a baseline rather than guessing.
A pelvic examination, sometimes done while you stand or bear down, shows the grade and which compartment is involved. That is the starting point for the practical steps: pelvic floor training that is taught properly rather than assumed, treating constipation so you are not straining, and sensible advice on lifting.
The type of birth is a conversation to have with your obstetrician, and it depends on your history and the grade rather than on the word prolapse alone. In selected cases a pessary can be used during pregnancy.
If you are planning another pregnancy, an assessment beforehand gives you the baseline and a plan, which is more useful than reassurance in either direction.