There is no set time for how long a new born premature baby stays in the hospital, however the most common rule of thumb is the earlier the baby is born, the longer they are required to stay and finish necessary developments. When a preemie is required to stay at the hospital after birth, they will be held in the Neonatal Intensive Care Unit (NICU) where they can safely receive the treatment they need to stay healthy. The average time a premature baby will spend in the NICU before they come home ranges on the low end of 2 to 3 weeks to in extreme cases a few weeks past their own expected birth due date.