baby who had a heart problem

I had a new born baby who the doctors say he die from a hole in his heart. I had no signs of that during my nine months of pregnancy and that was not detected at all by my doctor during my nine months of pregnancy. What could be the cause of him to died

[30something13]

if the dr said he had a hole in the heart that is what he died from, did they not do a late ultrasound on the baby? Like around 20-24 weeks? They can usually see that on there, but I have heard of them not seeing it if the hole is small.

So sorry for oyur loss, I lost a baby girl right after birth myself, it is very hard to deal with