Q. How does the NICU staff determine that a baby is ready to be discharged?
A. A healthy premature baby is in charge of when he or she goes home! In general, three major milestones need to be achieved: The baby needs to be taking good volumes of milk by nursing or bottle feeding and gaining weight consistently, he or she needs to be able to keep his or her temperature in the normal range without an external heat source (the isolette), and he or she needs to remember to breath while sleeping (ie, stop having apnea). Usually these things all happen about three weeks before the mother's due date. However, like all developmental milestones, there is a wide range of what is normal. So you shouldn't be worried if your baby takes a little longer to do these things.
In most NICU's, there is no specific weight your baby has to be to go home. However, most babies are at least 4 pounds, and more likely nearing 5 pounds when these milestones occur.
In some cases, babies may have medical problems that mean extra time in the hospital. For instance, if your baby needs oxygen, it is likely that he or she will be in the hospital longer--maybe even after the mother's due date. Physicians vary widely in their philosophies about home oxygen therapy, so it is good to ask your neonatologist early so you know what milestones to look for. The same holds true if your baby hasn't stopped having apnea (long breathing pauses). Some doctors prefer to send babies home earlier with a home monitor and medication, and some prefer to wait it out in the hospital for a few extra days. So ask your neonatologist.