I already have a 4yo dd and while trying for no.2 I've had a late term loss followed by 2 misscarriages. The one that annoys the most is "well at least you have dd" as if I just forgot how incredibly lucky I feel to have her. I'm thankful everyday for her but it doesnt take away from the pain of my losses
This isn't something commonly heard I suppose but my friend saying to me when finding out she was pregnant "oh I'm not getting my hopes up who knows what will happen" I think it just bugged me because she thought it would make me feel better that she was pregnant and I wasn't. I had only misscarried a month beforehand. As if id ever wish what I'd been through on anyone.
I agree the best thing to say is just I'm sorry for your loss and a hug.