In 95% of all cases miscarriage is the result of preexisting condition of the embryo. Often this is the result of a chromosome disorder caused during conception. Nature looks for a “ solution” and the pregnancy ends in a miscarriage.
Usually, this is not the result of a hereditary condition. Hence, there is no increased risk for a subsequent pregnancy. In 5% of the cases the miscarriage is the result of an improper nidation, infection, aberrant shape of the uterus, a myoma or unknown cause. When a woman has had two or more miscarriages it is possible to have further examination done.
You cannot cause a miscarriage yourself. A miscarriage is not the result of physical exertion, making love, falling or, for example, horseback riding. It can, however, be the trigger for an already existing miscarriage, to start.
A miscarriage can't be stopped or prevented.