Growth failure in infants may be diagnosed erroneously because of artifact, error, or both. Assuming that all full-term infants have the same gestational age creates an artifact that is confounded further by errors in measurement of birth length. Crown-heel lengths of 77 while full-term newborns born at the University of Kansas Medical Center, Kansas City, were plotted on standard National Center for Health Statistics postnatal growth chart percentiles appropriate for sex, both with and without regard for gestational age. By the end of the first postnatal year, significantly fewer downward shifts in the growth curves occurred when fetal age was considered in the location of birth percentiles, according to tables by Miller and Merritt. To avoid confusion in interpretation of downward shifts in infants' growth patterns, we recommend that accurate crown-heel lengths be obtained at birth and plotted according to gestational age whenever possible.