Baby announcement ethic opinion

Hi everyone!

So we are announcing our pregnancy this weekend at my daughter's birthday party. One of her friends mom's previously told me about her struggles with infertility. She is coming to the party and I feel I should tell her we will be announcing that I'm pregnant ahead of time, as I don't want her to be blind sighted and potentially upset or it bring up hard feelings for her, it may anyway but at least she would know the announcement was coming. I don't know exactly what to say when I do tell her, but I'm wondering if you guys would do this and how? Thanks everyone!