A pacifier is one of your strongest allies in the NICU if your child is being fed by IV or G-Tube. In any pre-term or medically fragile infant you are up against oral aversion (avoidance of food or texture in the mouth).
Although oral aversion can’t always be avoided, introducing a pacifier very early on can help to strengthen the ‘sucking’ reflex and allow for practice of oral movement (tongue, lips, cheeks). I used a pacifier in the first week after my sons surgery- he had an NG tube (nasogastric-from nose to stomach). Make sure to ask for approval from your care team before introducing a pacifier, but know that NICUs stock tiny preemie pacifiers for this use. My son was a 35-weeker and exclusively on TPN/G-Tube fed for weeks, I feel strongly that his pacifier was very helpful in the development of his oral motor skills.
See link below for a definition of oral aversion (Emory University, 2015)