Hi J.. I understand your frustrations & concerns with trying to get your preemie "caught up" to standard milestones. My son was also born 8 weeks early (31-4/7 wks to be exact). It's definitely been an uphill battle for him to gain weight too. They didn't get the last two months inside us to pack on any layers of baby fat so it's WAY harder to get any fat built up now. My son has always been in the 5th percentile (or lower!) for weight, but he continuously gained so the Dr. was never concerned because his growth curve was even. (You probably know this already, but to really see how your little one measures up on the standard growth chart, you can adjust his age to his due date until 24 mos, but by 24 mos most preemies are caught up) And don't get too hung up on the growth charts & percentiles, each child grows differently. A good growth curve is more important & more specific to your child's development.
If you breast feed, have you considered talking with your Pediatrician about supplementing any of his milk? I breast fed & also fed my son expressed milk supplemented with Enfamil's EnfaCare formula during the day until he was 1 yr old. It's just a small amount of this formula added to breastmilk so one can lasts a long time. If your son is already on formula, EnfaCare is a special formula for preemies & low birth weight babies that gives them extra vitamins, minerals, & calories so I would talk to the Dr. about that. (Our Dr. office gave us a free 8 oz can to try before we bought) It's usually only used until 9 mos, but since your son is still on the petite side, it might be something to consider. My son is now on whole milk, but I still also supplement his evening milk with a scoop of Enfamil's Next Step formula in 7-8oz milk. His 18 mos check up was yesterday and he is now 22 lbs and finally in the 10th percentile! (yippee!)
You got some good advice in other emails too. I would definitely have his iron levels checked. (ours was an easy toe prick test) If your Dr. isn't concerned about the lack of weight gain over the last 3 months, it's probably nothing to worry about. However, if you're uneasy about it, follow your intuition.
Did your Dr. ask you to come back in for a weight check in a few weeks? It usually doesn't cost anything (no co-pay, no charge for office visit) & you don't usually have to set an appointment either since you're just popping in real quick for a nurse to weigh him.
One other thing I wanted to ask was has your little one started on solids yet, besides cereal? We started solids around 9 mos and my son really loved finger foods, so that's when I noticed his weight really start to increase.
Best,
R.