108 Chapter 5 Table 8. Predictive value of IGF-I for fat free mass at term equivalent age B (SE) ß p-value Included variables Constant -5204 (1370) 0.001 PMA (weeks) 146 (30) 0.59 < 0.000 Change in IGF-I up to week 4 (nmol/L per week) 4652 (1247) 0.44 0.001 R² = 0.581, p < 0.001 Backward regression model. Variables not included in the final model: gestational age at birth, week 4 IGF-I, change in IGF-I from birth to 36 weeks PMA. PMA: postmenstrual age Potential confounders Total caloric intake (kcal/kg/day) up to 36 weeks PMA was associated with fat free mass at termequivalent age (r 0.364, p 0.044, corrected for PMA at the time of body composition measurement). In multivariate analysis, including the change in IGF-I up to 4 weeks PNA and the change in weight SDS from 30 weeks onwards, caloric intake was no longer a significant predictor. There was no association between caloric intake and fat (free) mass percentage. Protein, fat and carbohydrate intake up to 36 weeks was not associated with body composition at term equivalent age. Comorbidities (NEC, LOS, BPD, ROP, IVH and PDA) were not associated with body composition at term equivalent age. Gender and ethnicity were not associated with body composition at term equivalent age. Discussion This study confirmed that, in preterm infants, the postnatal growth and IGF-I are associatedwith body composition at termequivalent age. In particular, higher IGF-I levels in the first month of life and more weight gain in that period were associated with a more favorable body composition at term equivalent age. Meanwhile a greater increase in weight, length or head circumference SDS after this window was associated with a higher fat mass percentage at term equivalent age. IGF-I and growth in the first month of life After preterm birth, nutrient supply is abruptly disrupted. Moreover, as the transplacental supply of essential growth factors stops, the preterm infant now solely relies on their own production of these factors. This leads to a drop in IGF-I and consequent decrease in the SDS for weight, length and head circumference. (14) Accordingly, our population showed low IGF-I levels and a decline in growth rate in the first weeks of life.
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