Factors Associated with In‐Hospital Growth Trajectories of Very Low Birth Weight (VLBW) Infants
Authors: Asbury Michelle , Unger Sharon , Ng Dawn VY. , Kiss Alex , Luk Yunnie , Bishara Rosine , Tomlinson Chris , Gibbins Sharyn , O'Connor Deborah L. 
Published: November 2023

Background

Optimal in‐hospital growth is associated with improved long‐term health and neurodevelopment in VLBW infants. Previous studies have examined many explanatory factors (e.g. birth characteristics, type of enteral feeding, nutrient intakes, and morbidity). However, few studies have systematically evaluated these factors together to examine growth rates over the entire in‐hospital course.

Objective

To examine associations between infant characteristics, morbidities, daily macronutrient and energy intakes, and in‐hospital weight, length, and head circumference (HC) trajectories over time.

Methods

316 VLBW infants from the GTA‐DoMINO (ISRCTN35317141) trial were included. Infant characteristics, morbidities, daily nutrient intakes, and weekly anthropometrics were collected prospectively from birth to 90‐days or until hospital discharge, whichever occurred first. Repeated measures linear regression models were used to assess the relationship between explanatory factors and anthropometric measures over time.

Results

Mean birth weight, length, and HC were 1021 (SD, 260) g, 35.7 (3.4) cm, and 25.1 (2.3) cm, respectively. At birth, mean gestational age was 28.0 (2.5) weeks and 13% of infants were small for gestational age. All macronutrient and energy intakes were associated with weight over time. Of energy and macronutrients, energy intakes showed the greatest association with mean weight gain during postnatal days 9–29 (2.5 g/kg/d, p<.0001); however, lipid intakes showed the greatest association with weight gain during days 30–90 (3.0 g/kg/d, p<.0001). From days 1–8, all macronutrient and energy intakes were associated with length over time (p‐values: 0.003–0.0005); however, no intakes were associated with length beyond day 8. Lipid and energy intakes were associated with HC over time during days 1–8 and 9–29 (p‐values: 0.01–0.007), but not beyond the first month. Infants fed >50% donor milk showed slower weight gain between days 9–29 compared to infants fed >50% formula (−0.9 g/kg/d) or mothers' milk (−1.1 g/kg/d, p<.0001); while the HC gains of infants fed >50% donor milk and mothers' milk were similar, they were slower than the HC gains of infants fed >50% formula. Of morbidities assessed, patent ductus arteriosus showed the greatest association with weight (−2.6 g/kg/d, p<.0001) and HC (−0.21 cm/wk, p<.0001) during days 9–29, while late‐onset sepsis showed the greatest association with weight (−1.6 g/kg/d, p<.0001) and length (−0.13 cm/wk, p<.0006) during days 30–90.

Conclusions

Daily macronutrient and energy intakes are associated with weight gain over time, regardless of postnatal age. Early, rather than late, nutrient intakes are associated with length and HC gains over time. Morbidities and the strength of their association with growth are dependent upon the infants' postnatal age during hospitalization.

Support or Funding Information

Funded by CIHR (MOP#102638; FDN#143233).