Announcing baby #2 while sister is struggling getting pregnant

Hi all, my sister is 8 years older than me and has been trying to get pregnant for 10 years now. She just had her second miscarriage when she was 6 weeks and at the time I was 11 weeks and hadn’t told anyone besides my husband I was pregnant. Now I’m 13 weeks with baby #2 and thinking about making it public but don’t know how to approach my sister. I know she’s really struggling because of the fertility stuff and I feel like my announcement will just be a stab in the heart. We are waiting until after Christmas at least so we don’t ruin her and her husbands Christmas but I don’t know what to do. Or when to do it. They have a follow up at their fertility specialist on the 4th of January I believe. So don’t know if that will bring them good or bad news. I feel so guilty that it’s difficult for some to get pregnant and for others it’s no problem at all. We figured it would take awhile to get pregnant since I was breastfeeding and the first month baby took 🤷🏽‍♀️ help. Timing. How to say it. I pulled her aside with my first pregnancy and we cried together and now I’ll have to do it again 😥 so many family members are getting pregnant and she isn’t. Ugh. My heart feels for her.