Well, this question has come up before, and people seem to be divided. On one hand, it’s illegal for them to even ask if you’re married or if you have kids, so it’s really none of their business. You could leave her out of it if you’re afraid of discrimination. On the other hand, do you really want to be at a medical school that is going to be unsupportive of your family priorities?
Whether or not to bring it up seems to be a personal decision. Some people write it into their statements and are very forthcoming, and others prefer to keep their family life private.