Calcium on heart

I went for my 20 week ultrasound and my sweet little princess did not want to cooperate! The us tech wasn't able to get everything she needed so she said I would have to come back in 4 weeks. She mentioned that she saw some calcium on her heart. She said since I had the extensive blood work done that she was not worried about this (it typically means Down syndrome). She said it was more like a having a mole (it's just a mark) . The midwife seemed more concerned than the us tech and said if it's still there when I come back in 4 weeks she'll refer me to a specialist. Has anyone else heard of this? Did your baby have this? Everyone I've told about it has been extremely puzzled! I was so shocked about it that I didn't think to ask more questions.