My little guy’s only a year old, but has consistently stayed in the 40-50% percentile for weight since he began treatment at 1 month.  Before that, he was underweight due to being undetected and untreated (he dropped from a healthy 7lb 12oz birthweight to 6lb 9oz at 1 month old!).  We plan to encourage physical activity beginning now, which will be true for as many children as we’re blessed with, whether they have CAH or not.