Both. IUGR babies are prone to have poor growth. Most continue to have slow growth in the months after birth, often leading to GI interventions such as increasing nutrient density of formula. This is to make up for the nutrient deficit present that an average infant's daily intake typically cannot surpass on its own.While the vast majority (80%) of IUGR and/or SGA (small for gestational age) do catch-up to reach sizes comparable to other children, this typically takes about two years. Many factors affect growth and stature, including any medical problems that led to her being small. For instance, this nutrient deficit and propensity to growth failure tend to be worse in infants who were also preterm (at 37+1 weeks, your daughter was born just two days further along than what we would consider "late preterm").The main things you can control and monitor at this point are her nutritional intake and feeding habits. For now, the baby's goal is to be improving in her percentiles, not worsening. I recommend working with the GI team on this goal. They will likely have you see a pediatric dietitian as well to help figure out how many calories she should be getting.Don't despair - this is more common than you would think. It doesn't mean you're doing anything wrong. You are working very hard and doing everything you can right now. Getting more hands on deck by bringing in a specialist's perspective only means more people in your daughter's corner trying to get her growing better.Most babies born with IUGR do catch up their growth by this age, so I agree with your pediatrician's concern. Increasing the concentration ("fortifying") her formula is a great first step, but it's worth seeing the pediatric GI to make sure there isn't something else going on. I'd suggest keeping track of about how much she eats in a 24-hour period as well, so the doctor can assess whether she's getting enough calories.
Could her delayed growth be a byproduct of the IUGR? Or is it more likely shes just not taking in enough calories per feed? Additionally, are there any questions that youd recommend I ask the pediatric GI doc? Thanks so much!