Head circumference growth among extremely preterm infants in Denmark has improved during the past two decades

Introduction: Treatment of extremely preterm and low birth weight infants is still evolving and improving. In this study, we evaluated if growth has improved from birth to two years of corrected age (CA) among extremely low birth weight (BW) and preterm born infants in Denmark. Methods: This was an observational study with comparison of head circumference (HC), weight and length growth in two Danish cohorts of extremely preterm (gestational age (GA) < 28 weeks) and extremely low birth weight (ELBW with a BW < 1,000 g) infants (A: 1994-1995 and B: 2004- 2008). Results: Infants in cohort A (n = 198) and B (n = 64) had a median GA and BW of 27 + 2 weeks and 948 g in A, and 27 + 3 weeks and 934 g in B. At discharge, infants in B compared with A had increased more in HC (p = 0.000), length (p = 0.008) and weight (p = 0.000). At two years CA, HC was still significantly larger in cohort B than A (p = 0.03), while no significant difference was recorded for length or weight. Conclusion: Growth during hospitalisation seems to have improved among extremely preterm and low birth weight infants from 1994-1995 to 2004-2008. This may be a result of improved nutrition in combination with improved intensive care during hospitalisation. Trial registration: For the 1994-1995 study, all eight regional Research Ethics Committees in Denmark at that time approved the study. The 2004-2008 study was approved by the Danish National Committee on Biomedical Research Ethics, and handling of data and registrations were approved by the Danish Data Protection Agency. Funding: Collection of data in the 2004-2008 cohort was supported by the Institute of Regional Health Services Research, the Egmont Foundation and the University of Southern Denmark. Collection of data from birth to two years of age in the 1994-1995 cohort was without financial support.