Does anyone have advice about how to talk to family about newly discovered congenital abnormalities?

Just got confirmation that baby's feet are abnormal (most likely rocker-bottom), and I am feeling very overwhelmed. One thing on my mind is how/when to tell family. There is obviously some stuff we have to process through on our own first, but I know the day will come that we need to talk to our folks. For those who have been through something similar (other congenital abnormalities), how did you navigate that conversation? My mom is very anxious about everything, especially with this baby, so I am most nervous about telling her and what her reaction will be. Any advice is appreciated!