Comparison of different growth curves in the assessment of extrauterine growth restriction in very low birth weight preterm infants

Preterm infants are at risk of extrauterine growth restriction (EUGR) and associated complications in the long term. Growth curves are important in assessing postnatal growth in these infants. The aim of this study was to determine the prevalence of EUGR in preterm infants and the factors associated with EUGR using two different growth curves.We retrospectively evaluated 596 preterm infants with birth weight ≤1500 g. Small for gestational age (SGA) was defined as birth weight <10th percentile for gestational age. EUGR was defined as discharge weight z score <-2. All z scores were determined using both the Fenton 2013 and Intergrowth-21st (IG-21) growth curves.The infants' median gestational age was 28 weeks (27-29) and median birth weight was 1080 g (900-1243). The prevalence of SGA was 9.2% with IG-21 curves and 5% with Fenton curves (p < 0.001). The median discharge weight was 2060 g (1860-2363). The prevalence of EUGR was significantly higher with the Fenton curves than with the IG-21 curves (38% vs. 31.7%, p < 0.001). The mean discharge weight z score was -1.82±1.29 with Fenton and -1.44±1.49 with IG-21 curves. In multivariate analysis, significant risk factors for EUGR according to the Fenton curves were SGA (odds ratio [OR]: 19.15, 95% confidence interval [CI]: 4.4-82.59), respiratory distress syndrome (RDS) (OR 1.64, 95% CI 1.12-2.4), late neonatal sepsis (LNS) (OR: 2.27, 95% CI: 1.5-3.44), and >16 days to full enteral feeding (OR: 1.8, 95% CI: 1.22-2.68). Similarly, independent risk factors for EUGR according to the IG-21 curve were SGA (OR: 16.3, 95% CI: 7.23-36.9), RDS (OR: 1.81, 95% CI: 1.16-2.83), LNS (OR: 2.29, 95% CI: 1.43-3.68), and >16 days to full enteral feeding (OR: 2.11, 95% CI: 1.38-3.23).The growth curves used for diagnosis may lead to differences in EUGR rates in intensive care units and the factors identified as associated with EUGR. At-risk infants should be evaluated for EUGR and their weight and nutritional support should be monitored carefully. Comparisons of long-term outcomes are needed to assess the suitability of growth curves used for EUGR follow-up.