How does Désirée come to the conclusion that her baby may be bi- or multi-racial? How does this add to the plot and mood of the text? Should this be an issue (think of the time period of the text)?

The baby gets a darker complexion as it gets older. This becomes problematic considering the entrenched racism of the South as well as Armand's own bigotry. This certainly adds to the dark suspense of the story. Obviously, this should not be an issue in today's world but sadly for some, it still is.