From what I understand, the NNC's growth charts are more forgiving especially if your baby is not quite that big. For instance, in the NNC charts, at 3 months, normal weight for a baby girl would be 4.5-7.5kg. However, if you check the CDC chart, at 4.5kg, your baby will be between the 5th and 10th percentile and I'm sure your pediatrician will be saying that you are not feeding your baby enough and will direct you to supplement. How's that for a confidence buster?
On the other side, if your baby is about 7kg, she would still be considered within the normal range under the NNC charts but be overweight in the CDC charts as she will be above the 95 percentile.
In Naima's case, she is almost 26 months and currently weighs about 28lbs. or 12.7kg. Using the NNC chart, the normal range for her age would be 9.4-15.4kg. In the CDC chart, it's at 10.25kg (3 percentile) to 15.5kg (97 percentile). I realize that the difference in the charts would really matter if your baby is on the borderline of underweight and overweight. And usually, it would mothers with borderline babies who would be more vulnerable to supplementation or eventual cessation of breastfeeding.