Telling a friend that's doing ivf

I'm pregnant and my friend is doing ivf implantation next week. She has one baby but had several failed implantations with him. When do I tell her? After it takes? Before they do the procedure? What if it doesn't take? Then when do I tell her. I'd rather her not find out on fb or would that be the easiest for her? no need to respond. Thanks for any info!