Variation in very preterm extrauterine growth in a European multicountry cohort.

Extrauterine growth restriction (EUGR) among very preterm infants is related to poor neurodevelopment, but lack of consensus on EUGR measurement constrains international research. Our aim was to compare EUGR prevalence in a European very preterm cohort using commonly used measures. Population-based observational study. 19 regions in 11 European countries. 6792 very preterm infants born before 32 weeks' gestational age (GA) surviving to discharge. We investigated two measures based on discharge-weight percentiles with (1) Fenton and (2) Intergrowth (IG) charts and two based on growth velocity (1) birth weight and discharge-weight Z-score differences using Fenton charts and (2) weight-gain velocity using Patel's model. We estimated country-level relative risks of EUGR adjusting for maternal and neonatal characteristics and associations with population differences in healthy newborn size, measured by mean national birth weight at 40 weeks' GA. About twofold differences in EUGR prevalence were observed between countries for all indicators and these persisted after case-mix adjustment. Discharge weight <10th percentile using Fenton charts varied from 24% (Sweden) to 60% (Portugal) and using IG from 13% (Sweden) to 43% (Portugal), while low weight-gain velocity ranged from 35% (Germany) to 62% (UK). Mean term birth weight strongly correlated with both percentile-based measures (Spearman's rho=-0.90 Fenton, -0.84 IG, p<0.01), but not Patel's weight-gain velocity (rho: -0.38, p=0.25). Very preterm infants have a high prevalence of EUGR, with wide variations between countries in Europe. Variability associated with mean term birth weight when using common postnatal growth charts complicates international benchmarking.

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Competing interests: None declared.