As horrible as it sounds, necrotizing enterocolitis, often just called NEC, is where part of the intestinal is injured or dies.  It seems to develop when feedings are introduced into a vulnerable intestine with an area of diminished blood supply.  That vulnerability seems to be increased by bacteria in the intestine and any increase in the thickness or calories of the feedings.  The lining loses its blood flow or develops an infection and babies who are ill or premature don't have the immune systems and capability to fight this off on their own.  Their feedings need to be stopped, antibioti

To feed from breast or bottle, it takes an ordered, coordinated pattern of sucking, swallowing, and breathing. Without that pattern, babies can aspirate breast milk or formula into their lungs. Most infants can manage that by 34 weeks of age, some slightly sooner.