If this were my patient, the most important item is that the baby has
normal development.  I would want to know her length and head circumference
percentiles.  She has tripled her birth weight, but some don't hold with
that as a good marker for growth.  On the old fashioned charts, her weight
is 50% for a 6 month old, and she is below the 5th percentile, which is why
the doctor is probably concerned.  I would also want to know how big her
parents are and if there is familial constitutional growth delay in the
family.  Also, what are her stools like (thinking cystic fibrosis).  If
these  things are all reassuring, I would watch the baby.  If there was
anything worrisome, I might consider checking for anemia (CBC), liver or
kidney function and protein absorption and production (biochem panel) and
check how her bones are growing (bone age), maybe look at her urine to see
if she's wasting acid (urinalysis).

Terry

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