Potential Causes of Extrauterine Growth Failure in Premature Infants Born Appropriate for Gestational Age

Background: Extrauterine growth restriction (EUGR) is multifactorial in etiology and predisposes infants to multiple morbidities that can be significantly ameliorated by adequate nutrition and appropriate longitudinal growth. Current strategies to reduce the risk of EUGR include optimization of parental nutrition, varying schedules of feeding advances, and caloric supplementation. Very low birthweight (VLBW) preterm infants are particularly affected by EUGR, therefore ensuring adequate postnatal growth is an essential component in improving the long-term health outcomes for VLBW infants. The objectives of this observational study were to examine potential risk factors for growth failure among premature infants that did not respond to caloric and volume supplementation. Methods: We conducted a retrospective chart review of all infants born at the University of Massachusetts level III NICU from January 2016 to June 2020. Growth was tracked using PediTools electronic gestational age and growth calculators. (17) We reviewed the EMRs of infants who met the criteria for EUGR at the time of hospital discharge for a variety of potential factors affecting growth. Results: Overall, a total of 448 infants were screened with a final study cohort of 358 infants, of which 13% were discharge with EUGR. Analysis of demographic and clinical characteristics of infants with EUGR before and after nutritional intervention showed no statistically significant differences between the two cohorts. Pre-protocol, only weight percentiles and z-scores were statistically significant. Post-protocol, the change in z-score was also statistically significant. The only factor found to be statistically significantly different between was Necrotizing enterocolitis (NEC). Timing of EUGR in the pre-protocol groups occurred between 33-35 weeks, while in the post-protocol group EUGR occurred between 32 and 37 weeks (Figure 2). Conclusions: Our findings confirmed the presence of several factors that have been previously shown to increase risk for EUGR, including male sex, lower gestational age, lower birth weight, and the occurrence of NEC. It also identified an additional risk factor, that of being born “constitutionally small”. In the post-protocol cohort, the change in z-score was statistically significant in addition to birth weight percentile and z-score and discharge weight percentile in z-score. The window in which EUGR occurred as well as the interquartile range was significantly widened post-protocol. These data suggest that the volume supplementation protocol successfully addressed the causes of EUGR in some infants, but other mechanisms may have occurred in infants who were still discharged with EUGR post-protocol