Quoting ECT:" My daughter was 20'' at birth! She hasn't even grown 5 inches in 6 months lol"
How does the pediatrician measure her? It's really hard to get an accurate height for infants. When DS was 9 months he measured an inch shorter than his previous appointment, they figured it wasn't right so they tried again an was around 1.5 inches taller than his previous appointment lol. I've never taken their heights too seriously.
Measurement are way more accurate when the child can stand and be measured standing up.