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NEONATAL SOCIETY ABSTRACTS

Effect of maternal obesity on newborn body composition

Presented at the Neonatal Society 2009 Summer Meeting (programme).

Ruager-Martin R1, Thomas EL2, Uthaya S1, Bell JD2, Modi N1

1 Section of Neonatal Medicine, Division of Medicine, Chelsea & Westminster Hospital campus, Imperial College London, London, SW10 9NH, UK
2 Molecular Imaging Group, Medical Research Council Clinical Sciences Centre, Hammersmith Hospital campus, Imperial College London, London, W12 0NN, UK

Background and Aim: In searching for the biological mechanisms involved in development of obesity related metabolic co-morbidity, researchers have noted the relevance of early-life effects on location of adipose tissue depots, in addition to total adipose tissue quantity. The aim of this study was to test the hypothesis that infant body composition is associated with maternal body mass index.

Methods: We tested this hypothesis using our database of newborn infants in whom we have carried out whole body magnetic resonance imaging (MRI) as previously described (1). All the infants included in the analysis were term born singletons of non-diabetic, non-smoking mothers. All studies were approved by the regional ethics committee and written parent consent was obtained.

Images were analysed blind to the patient identity and study group. Total body adipose tissue was divided into 6 compartments: superficial subcutaneous (abdominal and non-abdominal), deep subcutaneous (abdominal and non-abdominal), internal (abdominal and nonabdominal). Adipose Tissue Mass (ATM) was estimated using the following formula: adipose tissue volume in litres x 0.9 = adipose tissue in kg. Lean body mass (LBM) was estimated as the difference between body weight and total body ATM. Infant pondreal index was calculated as Body Weight (kg) / Length(m)3. Correlation analysis was performed relating infant adipose tissue volumes and LBM to maternal pre-pregnancy BMI. In order to have 80% power to detect a correlation of 0.5, 29 subjects would be needed. All analysis was performed using SPSS version 16.0 (SPSS, Chicago, IL) Statistical significance was defined as p < 0.05.

Results: To date we have analysed data from 60 mother- infant pairs (30 boys and 30 girls). All the infants included in the analysis were singletons of non-diabetic, non-smoking mothers. The infants had a mean (sd) birth weight of 3.38kg (0.47) and gestational age of 40.3 weeks (1.1). The mothers had a mean pre-pregnancy weight of 63.7kg (10.4), height 165.5cm (0.08) and BMI 23.4 (3.9). 40 (65%) of the women were nulliparous. There was a highly significant negative correlation between maternal BMI and infant LBM (r = -0.35, p = 0.005) Maternal BMI remained significantly predictive of infant LBM after adjusting for actual postmenstrual age at the time of imaging (p= 0.017), but this effect diminished after also adjusting for infant sex (p = 0.07). No significant correlation was found between maternal BMI, infant ponderal index or any of the adipose tissue compartments. PMA at imaging, gender and maternal BMI accounted for 27% of the variance in newborn LBM.

Conclusion: Rising maternal BMI influences infant body composition in the term born infant. As the maternal BMI raises the LBM compartment is compromised.

References
Harrington TA et al Lipids 2002; 37: 951-57
Hull HR et al Am J Obest Gynecol 2008, 198: e1-e6.
Harvey NC et al. J Clin Endocrin and Metab 2006; 92; 523-26

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