M.T.
Deciding between preemie and newborn sizes really depends on how small the baby is to start with. A 5 lb baby will probably be out of preemie much faster than a 3 lb baby. My nieces were both early (only one a "preemie") and small. They actually did get a fair amount of use out of the preemie clothes (months). There is a fairly limited supply of preemie clothing available and the stores tend to overlap with what they carry. I bought outfits at Target.