[CA, P, AND MG POSTNATAL METABOLISM AND REQUIREMENTS IN PARENTERAL AND ENTERAL NUTRITION OF PREMATURE INFANTS]. / CA, P ET MG : MÉTABOLISME POSTNATAL ET BESOINS NUTRITIONNELS CHEZ LE PRÉMATURE EN ALIMENTATION PARENTÉRALE OU ENTÉRALE.

During the last trimester of gestation, transplacental mineral transfer and fetal mineral accretion is particularly high: 2.3-3.2 mmol/kg/day (90-130 mg/kg/d) of calcium, 2.4-2.7 mmol/kg/d (65-75 mg/kg/day) of phosphorus and 0.12-0.20 mmol/kg/d (2.9-4.8 mg/kg/day) of magnesium. After birth, there is a dramatic change in bone mineral metabolism from a maximal bone deposition during fetal life to a postnatal bone turnover stimulation improving bone structure and resistance. This physiological change could partly reduce the mineral requirements, as minerals available from the remodeling activities could be recycled for bone mineralization. In addition, recent studies in preterm infants, suggest that the use of early more "aggressive" nutritional support, providing high aminoacid intakes from the first day of life, may induce a "refeeding like syndrome" suggesting that early phosphorus and electrolytes supplies are also necessary. The aim of the present paper is to review the mineral metabolism of Very Low Birth Weight (VLBW) infants during the first weeks of life at the light of the more recent studies and to revise the nutritional recommendations for mineral parenteral and enteral intakes in VLBW infants.

Prematurity and bone health.

Recent advances in neonatal care significantly increases survival rate in preterm and particularly in extremely low birth weight infants (ELBW infants) and nutrition is becoming one of the most challenging issue to improve short and long term health and developmental outcomes. Nutrition is also relevant for bone development and mineralization reducing the risk of osteopenia and metabolic bone disease (MBD). Osteopenia of prematurity is a multifactorial disease including predominantly nutritional but also biomechanical and environmental factors. At birth, the fetal active mineral transfer is interrupted and the preterm becomes related to the parenteral and enteral mineral supplies. On the other hand, physiological adaptation of bone to extra uterine life leads to an increase in bone resorption. This process occurring earlier in preterm than in term infants can be accompanied by an increased risk of bone fragility and fractures. Early provision of highly bioavailable mineral supplies, correction of vitamin D deficiency and the screening of serum phosphorus concentration combined to urinary mineral excretion appears to be helpful for the prevention of MBD. When available, DEXA is more sensitive than ultrasound for quantifying osteopenia in VLBW infants at the time of discharge. Catch-up of mineralization is rapidly observed during the post term period and osteopenia of prematurity seems to be a self-resolving disease although the potential long-term consequences on the attainment of peak bone mass remains uncertain.