THE FALLACY OF “CATCH-UP” GROWTH IN PREMATURE INFANTS

Abstract

Growth data of 111 premature infants followed for 3 years were analyzed to determine if there is validity to the concept of catch-up growth. Weight, height and head circumference were recorded at each visit and converted to Z scores((X-X)/SD) to facilitate comparison of differing and sex. The of a child at each visit was for prematurity by subtracting the number of weeks premature from the post-natal to generate a Post-conceptual age was used to create new Z scores for all growth parameters at each visit. RESULTS: Growth data evaluated in the traditional manner suggested catch-up growth by one year of age. However, data corrected for age tended to resemble the growth of full-term children. The corrected growth data of AGA children almost completely approximated normal expected growth, whereas SGA children still demonstrated abnormal growth at 3 years of age, despite correction. SGA females tended to approximate normal growth after correction, whereas SGA males did not. The most significant finding of this study was that when corrected data were plotted on conventional growth charts, the apparent catch-up growth was found to be a statistical illusion created by charting growth of premature infants using post-natal instead of post-conceptual age. This finding has important implications for the follow-up of premature infants and may affect the interpretation and diagnosis of failure-to-thrive.