The term Ashkenazi refers to individuals descended from the medieval Jewish communities of the Rhineland in the west of Germany. Many Ashkenazi Jews (AJ) migrated to other parts of Europe, with the majority migrating eastward.

The conditions for which carrier screening is offered are more common in individuals of Ashkenazi Jewish descent than other ethnic groups because of specific mutations that occurred in "founders" of the population. Because Jewish individuals historically married within their own ethnic group, these mutations increased in frequency over generations.