Background: Knowledge of long-term growth of extremely preterm infants in relation to gestational age is incomplete, and there are concerns regarding their poor growth in early childhood. As part of a longitudinal study of a national cohort of infants born at <26 weeks' gestation (extremely immature), growth development from birth to the age of 11 years was examined, and correlates of growth attainment were analyzed.
Methods: Two hundred forty-seven extremely immature children were born alive from April 1990 through March 1992 in the whole of Sweden, and 89 (36%) survived. Growth and neurosensory outcomes of all extremely immature survivors were evaluated at 36 months of age. Eighty-six (97%) extremely immature children were identified and assessed at 11 years of age. In this growth study, 83 extremely immature infants (mean [SD]: birth weight, 772 g [110 g]; gestational age, 24.6 weeks [0.6 weeks]) without severe motor disability were followed up prospectively from birth to 11 years old and compared with a matched group of 83 children born at term. z scores for weight, height, head circumference, and BMI were computed for all children. We also examined gender-specific longitudinal growth measures. Predictors of 11-year growth were studied by multivariate analyses.
Results: Extremely immature children were significantly smaller in all 3 growth parameters than the controls at 11 years. Extremely immature children showed a sharp decline in weight and height z scores up to 3 months' corrected age, followed by catch-up growth in both weight and height up to 11 years. In contrast to weight and height, extremely immature children did not exhibit catch-up growth in head circumference after the first 6 months of life. The mean BMI z scores increased significantly from 1 to 11 years in both groups. The mean BMI change between 1 and 11 years of age was significantly larger in extremely immature than in control participants. Extremely immature girls showed a faster weight increase than extremely immature boys, whereas catch-up growth in height and head circumference was similar in these groups. Multiple-regression analyses revealed that preterm birth and parental height were significant predictors of 11-year height, and group status (prematurity) correlated strongly with head circumference.
Conclusions: Children born at the limit of viability attain poor growth in early childhood, followed by catch-up growth to age 11 years, but remain smaller than their term-born peers. Strategies that improve early growth might improve the outcome.