Honestly if you were my sister/daughter and you didn't have health issues I still wouldn't expect you to fly back. It's a long way. It's a lot of effort and money. I wouldn't want my girls to do anything that upset them for me.
I would stay home and keep trying to conceive. Ring your family and have them hold the phone up to her. Send videos of yourself for them to play with her.
I know you feel guilty, but I honestly think you don't have to.