SIL miscarried. How to talk about baby

Natalie
Hubby and I just found out his brother and wife miscarried. My mother in law told us and now the strange posts on Facebook and instagram make sense. We tried to contact them (they live in another state) after MIL said it was ok to call them but hubby got sent to voicemail. His brother didn't call back and my SIL text me the other day asking how my Dr. appointment went. She was due 2 weeks after me and I'm not sure how to go ahead about talking about my pregnancy. We haven't officially spoke to them which means they haven't officially told us but I'm sure they know we know. We find out the gender next month and I don't know how to reveal it to them without it bringing up bad memories. I know they're still excited for us but if I was in their shoes I'd still feel sad. I'm so lost as how to handle this.