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Extremely preterm birth results in altered body composition at age term-equivalent

Presented at the Neonatal Society 2003 Summer Meeting (programme).

Uthaya S1, Thomas EL2, Harrington T1, Bell J2, Modi N1

1 Division of Paediatrics, Obstetrics & Gynaecology, Faculty of Medicine, Chelsea & Westminster Hospital, Imperial College London, UK
2 Robert Steiner Magnetic Resonance Unit, MRC Clinical Sciences Centre, Du Cane Road, London, UK

Background and aims: Associations have been demonstrated between small size at birth and increased risk of adiposity and related morbidities in later life, but the epidemiological studies upon which these observations are largely based have not distinguished between preterm birth and intrauterine growth restriction as causes of small size. In adults and children intra-abdominal adiposity is associated with a spectrum of abnormalities known as the metabolic syndrome. Neither the age at which abnormal patterns of adipose tissue (AT) distribution become established, nor their determinants are known, though plausible determinants of increased intra-abdominal adiposity are rate of postnatal weight gain, type of nutrition and chronic glucocorticoid (GC) exposure. We have previously shown that in babies born at term, catch-up growth after intrauterine growth restriction is associated with a rapid increase in subcutaneous AT but not in intra-abdominal AT. The aims of this study are 1) to compare total and depot specific AT in preterm babies at the age of term equivalent and term-born babies and 2) to explore possible determinants of AT distribution.

Methods: We studied babies born <32 weeks gestational age when they reached the age of term equivalent and compared them with babies born at term. Total AT mass (ATM) and AT depots (subcutaneous and intra-abdominal) were quantified following whole body AT magnetic resonance imaging as developed by our group (1). We have previously presented details of this technique to the Society. We documented the number of days each preterm infant received breast milk, the number of days of level 1 intensive care (IC) (expressed as % of days of care) and weight gain by age term-equivalent (expressed as SDS gain; Child Growth Foundation). We used days of level 1 IC as a surrogate for endogenous GC exposure as we have shown that preterm babies in intensive care have a chronic elevation in circulating GC (submitted). Data were analysed using SPSS. This study has local research ethics committee approval and written parental consent is obtained.

Results: To date we have imaged 12 preterm and 31 term infants (table). The mean (SD) gestational age of the preterm infants at birth was 27.8 (1.9) weeks and the range was 25 to 31. The preterm infants weighed significantly less upon reaching age term-equivalent than the term born babies. There was no significant difference in total ATM as a percentage of body weight. However this masked a highly significant difference in the distribution of AT, with the preterm infants showing a greater proportion of AT in the intra-abdominal compartment.

Data are mean (sd)

Within the pre-term group univariate analysis showed ATM to be positively correlated with SDS gain (r=0.61; p=0.018) and negatively correlated with % duration of level 1 IC (r= -0.50; p=0.047) and % days receiving breast milk (r= -0.18; p= 0.28). However preliminary multiple regression analysis does not suggest that either total or depot specific ATM can be predicted from these variables.

Conclusions: Preterm birth alters the trajectory of adipose tissue deposition in comparison with term-born babies, with preferential distribution of adipose tissue in the intra-abdominal compartment. Further exploration is warranted to establish if these novel data can be explained by
postnatal nutritional support or other components of neonatal intensive care.

1. Harrington T, Thomas EL, Modi N et al. Lipids 2002; 37:95-100

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