Making the decision to breed from your mare should not be taken lightly. There are many unwanted and neglected horses that could have been avoided if people did not breed carelessly and without thought. Therefore I consider the primary question you should be asking yourself now is:
“Why are you breeding from your mare?”
Are you choosing to breed because your mare is a much loved pony that your family has now outgrown? If this is the case will the potential foal actually be suitable for your purpose or in fact be too small? Putting a big stallion to a small mare will not guarantee an offspring half way in-between - like humans they may take after the father or the mother. Before you breed because of sentimental reasons, ask yourself is your mare of good enough type or does she have faults that you are choosing not to see?
A common explanation I hear is that people are putting a mare in foal because she is too sharp or difficult in temperament to be ridden, which is a terrible reason to decide to breed. Temperament is certainly hereditary and a horse with a difficult nature is likely to pass this onto the foal, and even at a professional level, horses need to have both ability and a trainable disposition.
Breeding because of injury to the mare also needs to be considered carefully, as potentially the weakness or a predisposition to the injury may be directly hereditary or the conformational attributes that predisposed the injury may be inherited. If you have any concerns regarding this point you should discuss the situation with your own vet before proceeding.
Breeding to sell or breeding to keep? Sadly the notion that you can make lots of money breeding horses seems to rarely eventuate especially if you do not have your own property. The potential cost of breeding a single foal for you to keep is likely to far exceed the cost of buying one already grown. You need to consider firstly the cost of putting your mare in foal including veterinary fees and stud fees. Then you should add the potential livery costs for the mare while she is in foal, then with the foal at foot and once the foal is weaned. Where are you going to foal the mare down and how much will that cost? When do you plan to sell the progeny, as a foal, yearling or once they are being ridden and consequently what will the cost be of keeping them until that point? Will you insure the foal and what will the costs be for vaccinations, passport, microchipping, castration and other unexpected injuries or illnesses?
If you are planning on selling the offspring what is the realistic amount you are likely to get for them and how does this compare with the actual cost of producing a horse from birth to the point of sale? Even using the best of bloodlines for both the sire and dam does not guarantee a potential superstar and high value off-spring.
That said, there is nothing quite like the satisfaction of competing on a horse you have watched come into the world and produced through the grades yourself. In addition, not all horses have to be professional athletes and breeding from a sentimentally valuable mare to produce a pleasure horse that will be loved and have a happy home for life cannot be considered a bad thing to do. So if after considering the question "why are you breeding from your mare?", you are still keen to proceed then it is time to contact your stud veterinarian to discuss your individual situation.