Evaluation of and Recommendations for Growth References for Very Low Birth Weight (≤1500 Grams) Infants in the United States

Abstract

Objective. To determine the best available growth reference for evaluating the growth status of very low birth weight (VLBW; ≤1500 g) infants in the United States. Methods. We evaluated currently available growth references for VLBW infants in studies by Casey (Infant Health and Development Program [IHDP]), Brandt, Gairdner and Pearson, and Babson and Benda. We selected the 1 that best met a priori criteria and compared it with the new Centers for Disease Control and Prevention (CDC) growth charts. We evaluated the performance of both the selected VLBW reference and the CDC growth charts for use with VLBW infants by plotting data from 2 external data sets of VLBW infants (from Child Health and Development Studies [CHDS]) and linked the CDC’s Pregnancy Nutrition Surveillance System/Pediatric Nutrition Surveillance System Data (PNSS/PedNSS) on both references. Age was adjusted for gestational age in all of the VLBW data set comparisons. Results. The IHDP reference met the greatest number of our evaluation criteria. The IHDP charts are the most recent, are based on a relatively large sample of VLBW infants in the United States, and are adjusted for gestational age at birth (using the standard of birth at 40 weeks) to account for prematurity. The IHDP VLBW infants, based on corrected postnatal age, compared with the non-VLBW infants included in the new CDC growth charts showed more rapid growth in length-for-age from birth (40 weeks) to 24 months, were nearly equivalent in weight-for-age at birth (40 weeks), yet demonstrated less rapid growth in weight-for-age from 40 weeks to 24 months. The performance evaluation of the IHDP and CDC growth reference based on the 2 external VLBW data sets (CHDS and PNSS/PedNSS) showed that the IHDP charts more closely matched the external data sets in relative position on the graphs and growth patterns for length-for-age, but the CDC growth charts more closely matched the external data sets in the growth pattern for weight-for-length. In weight-for-age, because of the lack of stability in the pattern, we could not determine which reference the external data growth pattern more closely matched. Conclusions. Our evaluation of growth references for VLBW infants yielded no clear, simple recommendation. The inconsistencies in the discrepancies across anthropometric indices between the 2 external combined VLBW data sets (CHDS and PNSS/PedNSS) and the IHDP reference and the CDC growth charts make it difficult to recommend 1 reference. Therefore, we recommend using either the IHDP reference or the CDC growth charts to evaluate the growth of VLBW infants. The choice of which to use depends on its purpose. The IHDP reference is the best available reference for comparisons of the growth of a VLBW infant with those of other VLBW infants. The CDC growth charts allow comparison of the growth of a VLBW infant with that of non-VLBW infants.