What is the major reason why very-low birthweight babies are in grave danger from the moment they are born?

The lower the birth weight the greater the risk for health complications. Lower weight babies tend to be premature meaning that they haven't reached full development and are in danger from the moment they are born as they could have low oxygen levels in the body meaning they might not be able to breath properly when they are born. They could have infant respiratory distress syndrome as a result of immature lungs.