Some of these risk factors can be predicted before the onset of labor. If you are currently pregnant and fall into one of the categories that pose a higher risk of postpartum hemorrhage, you will not be able to prevent heavy bleeding... but you can ensure that you are in a location where you will be cared for properly if hemorrhage does occur.
While homebirth midwives and freestanding birth centers do often have treatment such as Pitocin on hand, women who need more serious intervention (like a blood transfusion, and sometimes even a hysterectomy) will greatly benefit from being inside a hospital. It is helpful to keep in mind that a hemorrhage can suddenly start in the days after birth as well, and not just immediately after delivering a baby.
It is not generally a concern, because it only happens in five percent of all births. But, due to the serious nature of a postpartum hemorrhage, it is good for every woman to be aware of this possibility in advance, consider it in their decision-making process about where to give birth.