The Impact of Estimated Energy and Protein Balances on Extrauterine Growth in Preterm Infants

Abstract

Background: Nutritional support of preterm infants remains a field of debate in the literature and clinical practice varies significantly. Adequate nutrition should promote growth and aim for optimal later neurodevelopment. However, it is often impaired by prematurity-associated morbidity and the physiologic immaturity of preterm infants. This study assessed the impact of energy and macronutrient provision on growth velocity and outcome and explored differences attributed to the heterogeneity of the preterm population.

Methods: We retrospectively collected clinical and nutritional data from neonates hospitalized in two separate Neonatal Intensive Care Units (NICUs). Estimated energy and protein balance were calculated based on the ESPGHAN guidelines and their association with the growth outcome was explored. Growth assessment was based on somatometry Delta (Δ) z-scores at discharge.

Results: In total, 174 neonates were included in the study. By day 14, most preterm infants were exclusively enterally fed, whereas there were infants in the <28 and 28-31⁺⁶ subgroups fed exclusively parenterally. Energy balance was positive for all gestational age (GA) subgroups except for those born <28 weeks. Protein balance was consistently positive for extremely premature but negative for late preterms. Cumulative substrates provisions were strong predictors of a positive energy or protein balance in the <34 weeks GA preterms on days 14 (ROC analyses, p < 0.001) and 7 (p < 0.05). A higher GA (p = 0.013) and enteral nutrition (p = 0.005) were additional predictors of a positive energy balance. All GA subgroups had a negative Δ z-score of weight at discharge. In the <34 GA subcohorts, a positive protein balance on day 14 (p = 0.009) and a short time to regain birth weight (exp(B) 3.1 (p = 0.004)) were independently associated with a positive Δ z-score of weight at discharge.

Conclusions: Early achievement of a positive energy and protein balance, based on the ESPGHAN guidelines, is crucial to ensure optimal postnatal growth and prevent extrauterine growth restriction, a relatively common occurrence in preterm infants.

Keywords: birthweight; energy; enteral; growth; neonatal; nutrition; parenteral; preterm; protein; weight z-scores.

Figure 1

Type of nutritional support across gestational ages on Days 3 (A), 7 (B), and 14 (C). The p-values express differences among all age groups.

Figure 2

Longitudinal distribution of various types of enteral feeding across gestational ages on Days 3 (A), 7 (B), and 14 (C). The p-values express differences among all age groups.

Figure 3

Cumulative distribution of provided (A) energy, (B) protein, (C) carbohydrates, and (D) fat through enteral and parenteral routes across gestational ages on days 3, 7, and 14. Substrates are expressed in g/kg/day and energy in kcal/kg/day. The p-values express differences among all age groups at different days (D3, D7, D14); BW = Body Weight; D = Day.

Figure 4

ROC analysis of a positive estimated energy balance on day 14 including (A) all gestational age (GA) subcohorts; (B) the smallest preterm infants with GA < 34 weeks; nutrition type indicates a lower to higher scale: enteral vs. parenteral vs. enteral and supplemental parenteral.

Figure 5

ROC analysis of a positive estimated protein balance on day 14 including (A) all gestational age (GA) subcohorts; (B) the smallest preterm infants with GA < 34 weeks.

Figure 6

Comparable anthropometry at birth and discharge in different GAs: (A) body weight, (B) body length, (C), weight z-scores and delta z-scores, and (D) length z-scores and delta z-scores. The p-values express differences among all age groups at admission and discharge.

Figure 7

ROC analysis of a positive Δ z-score of weight at discharge in (A) all studied infants (B) in the <34 GA subcohorts.