Your quibble is nothing more than another attempt to evade addressing the point directly. Most of the time, the careful driver will have no accidents. Most of the time, the careful woman will not become pregnant. However, it just takes once to counteract any number of previous successes. When that happens, the person involved must be able to choose from all possible solutions.
Abortion is obviously a solution.
The only person who should make the determination as to what solution may be acceptable for any given scenario is the person who is directly affected. In the case of an accidental pregnancy, that determination belongs to the woman and not to anybody else. Moral arguments are just one consideration among many that she must weigh in making her decision. People don't accidentally have sex, therefore, they don't accidentally make babies. That conclusion does not follow from your premise.