Body composition in very preterm infants during their hospital stay

Abstract

Background The survival of preterm infants has increased over the past decades. However, these infants are still at high risk of poor growth especially those born at <32weeks gestation (very preterm infants, VPT infants). The American Academy of Paediatrics recommends that the "postnatal growth of preterm infants in both their anthropometric indices and body composition should be the same as the normal fetus of the same gestational age". VPT infants at term equivalent age have been reported to have an increased percent body fat (%FM) and a lower fat free mass (FFM) when compared with term born infants. Nutritional and non-nutritional interventions during this period before term equivalent age have been closely associated with later growth but also with important neurodevelopmental and metabolic outcomes. Few studies in VPT infants have reported body compositional changes during their hospital stay and before term equivalent age. Aim The aim of this thesis is to assess growth and body composition, and to examine the nutritional and non-nutritional predictors of these, in VPT infants during their hospital stay. Methods Growth and body composition were assessed using air displacement plethysmography (PEAPOD) to measure %FM and FFM (g) in infants (n=113) born before 32wks gestation and studied at 32-36wks post menstrual age (Study Infants). Study infants were compared to a second group of preterm infants (n=88) born at 32-36wks gestation who were measured at two to five days post-partum, representing in-utero growth (Control group). Anthropometric measures for all infants included weight, length, head circumference, abdominal circumference and mid upper arm circumference. Actual macronutrient intakes of protein, lipid, carbohydrate and energy were calculated in VPT infants from birth until 34 weeks post menstrual age from the daily fluid records of parenteral and enteral intake. Infant morbidities and maternal characteristics were derived from infant and maternal medical records and examined for their effect on VPT infant body composition and growth. A %FM prediction equation for VPT infants was developed from the anthropometric measurements. Publications during candidature Conference abstracts [1] Al-Theyab N, Donovan T, Colditz P, Lingwood B. Ex-utero growth in infants born before 30 weeks gestation is associated with a significant increase in body fat.

Current practice in the introduction of solid foods for preterm infants

“…It has thus been suggested that any obesity association may be more of a risk in older gestational age preterm infants with no co-morbidities than in those of earlier gestational age (39) . More recently, researchers have identified that preterm infants have altered body composition, characterised predominantly by less fat-free mass but a maintained fat mass, leading to a greater percentage total body fat (13,40,41) . Further research into the childhood and later-life obesity risks of timing of the introduction of solid foods is required in these at-risk populations.…”