Why does Hester refuse to tell Pearl the truth about the meaning of the "A?"

Hester's refusal to tell Pearl the true meaning of the letter is symbolic of Pearl's role in the novel. Pearl has often been compared to a living version of the scarlet letter. Telling Pearl about the "A" would reveal something that Hester is afraid Pearl can not fully comprehend. I think Hester also doesn't want to, at this point, accept Pearl as her precious symbol of the "A".

Hester refuses to tell pearl the truth bout the letter A because she won't understand