Sorry to hear this. Don't want to be an alarmist. As a former NICU nurse there are many different types of congenital heart defects. The type of defect and the foetus's response in utero will determine the course of action to be taken before, during and after delivery. Neonatal heart specialists will be on hand during delivery and will manage immediate post birth care. Surgery might be required immediately after birth or within the first month or so. All depends on the type of defect and how the baby tolerates it. Delivery should be at a hospital that performs neo natal cardiac surgery. Difficult but you all and especially the mom to be should be as calm as possible, not consult Dr. Google and softer Wednesday results ask for a referral to a neonatal cardiologist to plan labour and delivery.
In todays world most babys prediagnosed before delivery have good outcomes. Mom should be referred asap and meet all the staff who will be involved with their care as soon as possible