Premature Infants with IUGR: Physical Development and Body Composition

Introduction: Premature infants with IUGR have higher risks of long-term metabolic and cognitive disorders due to disharmony of neuroendocrinal regulation of plastic processes; at the same time, differentiated approaches to nutrition of premature infants with IUGR with account of their postnatal physical development dynamics have not been developed yet. Therefore, the aim of this study was to compare physical development and body composition of premature infants with IUGR and without IUGR during the first 6 months of life.

Materials and Methods: A nonrandomized, controlled, prospective cohort, single-center clinical study of anthropometric parameters and body composition dynamics in 100 premature infants during the first 6 months of life was performed. Infants were assessed at term corrected age (38–42 postconceptual age [PCA] weeks), and at 3 and 6 months corrected age (CA). Infants included in the study were categorized into groups depending on the presence of IUGR/absence of IUGR and gestational age (GA): infants with IUGR and GA  <  34 weeks, infants with IUGR, and GA ≥ 34 weeks premature infants born adequate for GA. Anthropometric measurements were estimated by Fenton growth chart and Anthro (WHO, 2009); body composition was estimated by an air plethysmography system.

Results: Enrolled infants belonged to the following subgroups: infants with IUGR and GA  <  34 weeks (n = 30, GA = 32.30 [27.00–33.5] weeks, birth weight [BW] = 0.965 [0.722–1,280.00] g), infants with IUGR and GA ≥ 34 weeks (n = 30, GA = 36.08 [35.00–36.30] weeks, BW = 1,950 [1,800–2,130] g), and premature infants born adequate for GA (n = 40, GA = 33.60 [27.00–36.70] weeks, BW = 2,020.50 [0.630–3,050] g). At term CA, premature infants with IUGR and GA ≥ 34 weeks showed expressed decrease (“catch down”) of z-scores of weight (−2.54 [−2.68 − (−2.15)]) and length (−1.65 [−2.18 − (−1.52)]) (р  <  0.001) in comparison with premature infants  <  34 weeks. At corrected age of 3 months, it caused “catch up” associated with high proportion of fat mass (%) in body composition (26.1 [24.12–28.15]) compared with infants born  <  34 weeks (20.3 [16.20–28.80]) (р  <  0.001) ([Fig. 1]). Between corrected age of 3 and 6 months, slow increases of z-score for weight (−1.41 [−2.52 − (−0.45)] at 6 months) (plateau period) and continuing “catch up” of length (−0.73 [−1.53 − (−0.01)] at 6 months) (р  <  0.001) in premature infants with IUGR and GA ≥ 34 weeks were noticed. Significant increases of fat mass in body composition were not noticed in this period (26.9% [21.2–30.2] at 6 months). Premature infants with IUGR  <  34 weeks had a “catch up” at 38 weeks of PCA. At following periods, a trend toward moderate decrease of weight and length z-scores occurred. At corrected age of 6 months, fat mass (%) in body composition in infants with GA  <  34 weeks was higher than in premature infants  <  34 weeks (26.9 [21.2–30.2] compared with 18.25 [13.25–24.25]) (р  <  0.001). Nevertheless, at corrected age of 6 months, fat mass (%) in premature infants with IUGR was significantly higher than in premature infants born adequate for GA.

Conclusion: Opposite changes of plastic processes depending on GA are common for premature infants with IUGR during the early postnatal period. These data warrant further studies on feeding regimens, to better address the specific needs for individualized, tailored corrections of the nutritional supplies in premature infants with IUGR.

Keywords: premature infants, nutrition, body composition, fat mass

Fig. 1 Fat mass (%) change in premature infants depending on gestational age, presence/absence of IUGR, and postnatal age.