Anthropometric trends from 1997 to 2012 in infants born at ⩽28 weeks' gestation or less

Abstract

Objective: Postnatal growth failure is common after preterm birth, in particular for infants born at ⩽28 weeks' gestation, but it is unknown if growth-to-term equivalent age has improved over the years as neonatal intensive care in general, and infant nutrition in particular, have improved. The objective of the study was to evaluate anthropometric trends at NICU discharge for infants born at ⩽28 weeks' gestation using a large national database.

Study design: Analysis of growth in weight, length, head circumference and body mass index (kg m²) in 23 005 infants born in 1997 to 2012 who survived to neonatal intensive care unit discharge at ⩽41 weeks' postmenstrual age.

Results: Discharge weight, length, head circumference and body mass index were converted to Z-scores using a reference database, and growth trends over the 16 years were summarized. Discharge results also were summarized for common neonatal morbidities, including chronic lung disease. Gestational age at birth and postmenstrual age at discharge were similar across the 16 years. Discharge weight, length and head circumference Z-scores were all below the median, but head circumference Z-scores consistently were closer to the median than were weight and length. In 1997 compared with 2012, the weight Z-score improved from -1.5 to -0.6; the length Z-score increased the least, from -1.68 to just -1.16; the head circumference Z-score improved from -0.68 to -0.30; and the body mass index Z-score increased from -0.66 to 0.19. Percent small-for-gestational age at birth was stable across the years at 8.4 to 9.3%, and the frequency of postnatal growth failure at discharge improved from 55.4% in 1997 to 19.6% in 2012.

Conclusions: Growth-to-discharge progressively improved from 1997 to 2012, but Z-scores remained below the reference median for weight, length and head circumference. Length Z-scores were consistently significantly less than for weight, and body mass index Z-scores have been above the reference median since 2002. Prospective studies are needed to quantify anthropometric trends in relation to body composition and to current nutritional strategies.