Medical problems in baby

If a baby is born and has medical problems such as they are blind, deaf, etc, do the parents know beforehand from scans or do they find out afterwards when the baby is born ? 🤔

I am asking because I was born with cataracts, so I had vision problems and had surgery at 3 years old to get non - blurry eyesight . And I’m just so scared . My 1st baby is a healthy 15 month old with no problems at all. This is my 2nd .