Will nec cause lifelong problems?

Depends. It depends on the condition of the intestines. Most of the time it is only medical nec, means possibly no perforation. Even with perforation with timely intervention including bowel rest, antibiotics and surgery at apporpriate times can save the intestine. In the worst case senerio bowel resction may be needed that might cause the short bowel syndrome. Short bowel syndrome can have lifelong conse.