How does the revelation at the end of the story contribute to the storys theme

Here's a complete version of the question:

How does the revelation at the end of the story "Désirée's Baby" contribute to the story's theme?

The last line did not only reflect the racial theme of the short story, but also revealed the theme of a mother's love and how that love can instinctively affect the decisions you make later on in life.The racial themes are apparent first in the characters need to hide any kind of evidence that they have black blood. Even if people in the South knew you had a distant relative who was black, they would still view you as inferior to the white race. This is the reason the author suggests people didn't take to the beautiful Désirée. People didn't know her origins. The Valmondes found her as a baby, and although they did their best to put the rumors to rest, people still find it difficult to believe that she was purely white.

It is quite fascinating that Armand is not only bowled over by her but doesn't care about her origins. As the author states, “he was reminded that she was nameless. What did it matter about a name when he could give her one of the oldest and proudest in Louisiana?” Rather than follow his thoughts, he does what the author says all his family did and goes by his instincts.