Almost 1 of every 10 infants born in the United States are premature, or preemies. A premature birth is when a baby is born before 37 completed weeks of pregnancy. Because they are born too early, preemies weigh much less than full-term babies. They may have health problems because their organs did not have enough time to develop. It can be challenging to nurse a premature babies. Until about 32 weeks, babies can’t coordinate sucking, swallowing, and breathing well enough to breast or bottle feed, and babies less than about 37 weeks aren’t strong enough to take enough nutrition by mouth to gain weight. Moms who chose to breast feed need to use breast pump and tube feeb their babies.

I found a very useful article on this with great tips on breastfeeding premature babies.

https://www.verywell.com/tips-for-breastfeeding-a-premature-baby-2748577