head circumference

sandstar10

This week at my LO's 2 month checkup the pedi checked length, weight, and head circ. Her length is in the 90 percentile, weight in 50 percentile, but head circumference only in the 10th percentile.  The pedi said all is well since it is growing steadily and on a curve from the last checkup but I got myself worried since I read low head circum could mean slow brain growth.....anyone know anything about this?  Should I worry?