Our son was born 8 weeks early and weighed 4 lbs 1.8 oz.  He was in the hospital for 8 weeks, but never needed a respirator.  One of our worries was that he would contract RSV, which is a respiratory disease.  We did not take him out of the house for one year (except for Dr appts.) and we did not allow a lot of people to come over to the house to hold him.  Developmentally, he was behind until about 2 years old, and now he is a normal little boy.