growth spurt

For the first couple of years, Benjamin was 90th percentile for height. Then at his 3yo checkup, he was suddenly 50th percentile. The doctor acted as if that was fine. He's average, after all, right? But when I pointed out the vector, he understood my concern. The nurse measured Benjamin at 37.5" at the time. That was the same result we got at home, so the doctor told us to keep measuring him and see if he progressed at about 2 inches per year. Only three months later, Benjamin has already grown almost 2 inches! Tonight we measured him at 39.25". A web calculator I found says that that's 82nd percentile for a 39-month-old boy. (But that same web calculator says he was 60th percentile in July.) Anyway, that's quite a growth spurt.