Parents should learn everything they can about their baby's condition after they've had time to process their emotions.
One thing parents need to understand about the diagnosis is that doctors can only provide an average life expectancy -- and no individual is exactly average. Parents can sometimes be just as distressed if a baby surpasses his life expectancy as they would be if he didn't reach it. This distress is caused in part when they don't know what to do with their child if he lives longer than expected. For this reason, contingency plans should always be in place.