Renal proximal tubular function was assessed in neonates by measuring urinary beta 2-microglobulin (beta 2M) concentrations on days 1, 4, 7, 14 and 28. Values were elevated in stable preterm low-birthweight (LBW) neonates but not in stable term LBW neonates, suggesting that proximal tubular maturation is related to gestational age rather than birthweight. The urinary beta 2M was significantly increased on day 1 in neonates with the meconium aspiration syndrome but was not significantly different from normal subsequently. This indicated that although the proximal tubular cells may be susceptible to perinatal hypoxia, they maintain a remarkable capacity to recover in a relatively short period. Neonates with transient tachypnoea of the newborn had normal urinary levels of beta 2M indicating their renal tubular function was not impaired.
The bone mineral status of very low birthweight (VLBW) infants fed exclusively their own mother's milk (group I) was compared with that of VLBW infants fed mother's milk in the initial 4 weeks followed by a 1:1 mixture of mother's milk and preterm formula containing high phosphorus (P) and calcium (Ca) (group II). In both groups, most infants showed a biochemical picture characteristic of phosphorus deficiency syndrome by the fourth week. Thereafter, serum alkaline phosphatase activity (ALP) decreased and serum P increased in all group II infants. Conversely, serum ALP rose and hypophosphatemia persisted in most group I infants. Group II had a significantly higher serum P at weeks 8 and 12 and a significantly lower ALP at week 12 than group I. Furthermore, group II had a lower incidence of severe radiographic abnormalities than group I at week 12. We confumed previous observations that VLBW infants fed exclusively human milk require P and Ca supplementation to prevent metabolic bone disease of prematurity.
Biochemical and radiographic abnormalities linked with phosphorus deficiency syndrome (PDS) developed in two very low birthweight (VLBW) infants fed exclusively with human milk. By increasing phosphorus (P) and calcium (Ca) intakes with the introduction of a specialized premature formula, osteopenia or rickets, as well as hypophosphatemia, hypo‐phosphaturia and increased serum alkaline phosphatase levels improved in both patients. We speculated that all VLBW infants who are being fed exclusively with human milk should be monitored for PDS and that if PDS develops, supplementation of human milk with both P and Ca appears to be necessary for its treatment.
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