What generally happens to the dental arch as a result of premature loss of deciduous molars?

The premature loss of deciduous molars typically results in the loss of arch length. These molars play a critical role in maintaining the correct spacing for permanent teeth and providing stability to the dental arch. When they are lost too early, adjacent teeth can drift into the space left by the lost molars. This drifting often leads to a reduction in the arch length, as the teeth shift towards the midline in an effort to close the gap. Consequently, the alignment of the remaining teeth can also be affected, resulting in potential crowding, misalignment, or other dental issues.

The other options do not accurately describe the changes that occur. The arch does not become wider or taller as a direct result of the loss of these molars, nor does the shape remain unchanged; rather, it tends to become less stable and more susceptible to alterations in alignment and spacing.