Postnatal growth and body composition in extremely low birth weight infants fed with individually adjusted fortified human milk: a cohort study

Abstract

This cohort study aimed to evaluate the impact of an individualised nutritional care approach combining standardised fortification with adjustable fortification on postnatal growth and body composition in extremely low birth weight (ELBW) infants. We included ELBW infants admitted to a neonatal intensive care unit and still hospitalised at 35 weeks postmenstrual age (PMA). The fortification of human milk was standardised (multicomponent fortifier) between 70 mL/kg/day and full enteral feeding, and then individualised using adjustable fortification. When weight gain was below 20 g/kg/day, protein or energy was added when serum urea was below or above 3.5 mmol/L, respectively. Postnatal growth failure (PNGF) was defined as being small for gestational age at discharge and/or when the Z-score loss between birth and discharge was higher than 1. Body composition was assessed between 35 and 41 weeks of PMA. Among the 310 ELBW infants included, the gestational age of birth was 26.7 ± 1.8 weeks, and the birth weight was 800 ± 128 g. The mean Z-score difference between birth and discharge was moderately negative for the weight (-0.32), more strongly negative for length (-1.21), and almost nil for head circumference (+ 0.03). Only 27% of infants presented PNGF. At discharge, fat mass was 19.8 ± 3.6%. Multivariable analysis showed that the proportion of preterm formula received and gestational age at birth were independently associated with the percentage of fat mass. Conclusion: The individualised nutritional care approach applied herein prevented postnatal weight loss in most infants, limited length growth deficit, and supported excellent head circumference growth. What is Known: • At least half of extremely low birth weight infants are small for gestational age at discharge and postnatal growth deficit has been associated with impaired neurocognitive and renal development. • Human milk is the main milk used in neonatology and, although fortification of human milk is a standard of care, there is no consensus regarding the optimal fortification strategy to be adopted. What is New: • Using an approach combining standardised fortification followed by individualised adjustable fortification limited postnatal growth deficit for body weight and head circumference. Postnatal growth failure is not a fatality in extremely low birth weight infants. • Each additional gestational age week at birth resulted in a decrease in fat mass percentage at discharge, which was higher than in foetuses of the same gestational age, likely representing a necessary adaptation to extra-uterine life.

Keywords: Breastfeeding; Fat mass; Fortification; Nutrition; Prematurity.

Fig. 1

Flow chart

Fig. 2

Weekly protein intake a, energy intake b, and protein to energy ratio c in 310 extremely low birth weight infants between birth and discharge, expressed as mean and standard deviation. Grey zones represent recommended intakes (Ref. 15)

Fig. 3

Postnatal weight gain (g/kg/day) in 310 extremely low birth weight infants (a boys; b girls). The grey lines represent the Fenton weight gain curves, and the black lines represent the mean weight gain of the present cohort (solid line) + / −1 standard deviation (dotted lines)

Fig. 4

Differences in Z-score for body weight, crown-heel length, and head circumference between birth (light grey) and discharge (dark grey) in 310 extremely low birth weight infants. Expressed as boxplot (median, P25, P50, min, max)

Fig. 5

Fat mass (%) and fat-free mass (g) at discharge in 112 extremely low birth weight infants of the present cohort (dark black) compared to term infants at birth (white) and term infants at 2 months of age (grey). Reference values for term infants were obtained from ref. 10