It’s called AVSD and apparently means holes they need to close up
The repair depends on the size of the 'hole', this used to be called, "a hole in the heart".
For most babies it isn't even an operation it is a procedure done under anesthetic but is really simple.
A cut is made to access an artery (or vein), usually in the groin and a thin plastic tube is fed into the artery up to the heart.
A folded device is fed up the tube and into the heart where it is placed through the hole, this is then opened at both sides. If you imagine putting two umbrellas together at the top with the handles facing away and then open both umbrellas this is the type of shape.
They won't know until birth how big the holes are, well not the top hole anyway. This is because babies do not breath before they are born so ALL babies have a hole in the heart, at birth a flap folds down due to the pressure from the blood, normally it covers the hole entirely and becomes part of the septum wall.
A hole in the bottom chamber might need an operation, but this is something that has been done for years and is fairly routine. It depends on the size but the same technique can be used.
Some people born before ultrasound have lived completely normal lives and the holes are only diagnosed when they go to hospital for something else.
I've seen a man in his 30s who had two holes in his heart and no valve on one side, it was discovered in his 30s and as he was in good health was just monitored.
Link to a Dr who does this, it is written for the lay person so no fancy medical terms.
www.drebabucardiologist.com/post/asd-device-closure
I know saying 'try not to worry' is ridiculous, you are a mum and it is your job to worry but try to enjoy your baby.