Longitudinal changes in the bone mineral content of term and premature infants

With the use of photon absorptiometry, bone mineralization was measured at birth and 8 and 16 weeks after delivery in 12 very-low-birth-weight premature (mean +/- SD gestational age, 31 +/- 1.5 weeks) infants who required minimal medical support. Simultaneously, 19 healthy term infants were studied. Throughout the study, each neonate received modified 84-kJ/30 mL formula containing no added calciferol. The recommended daily allowance (400 IU) of calciferol was given to each infant as an oral supplement. Serum 25-hydroxyvitamin D, calcium, phosphorus, and parathyroid hormone concentrations were monitored biweekly and were normal. Bone mineral content and bone width significantly differed at birth between the term and premature infants. However, by 16 weeks after delivery, the premature infants had exceeded the bone mineral status of the term infants at birth, and their bone mineral content was not significantly lower than that of the term infants. These data indicate improved bone mineralization as compared with previously reported data from very-low-birth-weight neonates.     

Genetic determinants of bone mineral content in premature infants

Genetic determinants of bone mineral content in prematurely born children at 3 months and 9-11 years of age were studied. The findings suggest that multiple genes are involved in the regulation of site specific bone mass accumulation during childhood.     

Bone growth with low bone mineral content in very low birth weight premature infants

We report serial measurements of bone mineral content (BMC), bone width (BW, a measure of appositional bone growth), and the ratio of BMC:BW by photon absorptiometry of the left radius through the first 10 wk of life in 38 very low birth weight premature infants (birth weight less than 1300 g, gestational age less than 32 wk). Fifteen of 38 infants developed bronchopulmonary dysplasia (BPD) and as a group they could not be distinguished from the 23 infants without BPD, despite the high association between BPD and metabolic bone disease. As BPD occurred in the smaller patients, the BPD group had a significantly lower mean birth weight and mean gestational age as compared to controls (950 +/- 125 g versus 1119 +/- 149, and 28.0 +/- 0.8 versus 29.0 +/- 1.3 wk). For both control and BPD groups, BMCs did not differ and remained relatively unchanged throughout the first 10 wk of life, lagging significantly behind the intrauterine rate as defined by measuring BMC in 175 infants of varying gestational ages during the first few days of life. BW also did not differ during this period between groups. BW did increase significantly in both groups (from 3.2 +/- 0.3 to 3.9 +/- 0.4 mm in the controls and from 3.0 +/- 0.3 to 3.8 +/- 0.4 mm in the BPD group), but remained significantly delayed compared to the intrauterine rate. In both groups, BMC remained relatively constant despite increasing BW and thus BMC/BW decreased during the first 10 wk of life (from 11.5 +/- 1.3 to 10.2 +/- 1.9 in the controls and from 11.0 +/- 1.3 to 8.6 +/- 2.2 in the BPD group).(ABSTRACT TRUNCATED AT 250 WORDS)     

Bone mineral content in term and preterm appropriate-for-gestational-age infants.

Photon absorptiometry adapted for use in small infants was utilized to measure bone mineral content in 42 term and 30 perterm appropriate-for-gestational-age infants. BMC at birth correlated significantly with gestational age and birth weight. Sequential measurements of BMC in premature infants during the first three months showed that the postnatal increase in BMC was significantly less than the BMC expected in utero. We speculate that decreased intake of calcium and phosphate effects postnatal bone mineralization in premature infants.     

Measurement of bone mineral content in the term and preterm infant

We tested the best anatomic site, reliability, and reproducibility of single-photon absorptiometric bone density measurements in premature and term newborns. Humerus and radius measurements were compared using a commercially available densitometer. The humerus was a more reliable site of measurement, particularly in the very-low-birth-weight infant. Normal ranges of humerus bone mineral content (BMC) were defined for infants of 24 to 42 weeks' gestational age at birth. Humerus BMC correlated with gestational age and birth weight of patients. We conclude that bone densitometer measurements can be successfully performed, even in very-low-birth-weight infants, when the humerus is used as the measurements site. We define normal humerus BMC values for use in diagnosis and evaluation of efficacy of treatment in infants who are at higher risk for osteopenia of prematurity.     

Whole body bone mineral content is similar at discharge from the hospital in premature infants receiving fortified breast milk or preterm formula

BACKGROUND: Prematurely born infants, especially those with very low birth weight (<1500 g) are at risk for metabolic bone disease. OBJECTIVES: The influence of the type of oral feeding regimen and of other potential determinants of whole bone mineral content in prematurely born infants, when they approached full gestation, were evaluated. Previous studies have mainly examined effects at the level of regional bone. METHODS: 34 infants (21 males and 13 females), all born between 25.4 and 33.7 weeks of gestation, were studied before discharge. Whole body bone mineral content measurements were made just before hospital discharge using a commercial densitometer (Hologic QDR 4500, Hologic Inc, Waltham, MA) at a median age of 40 days (range, 10 to 115 days) after birth. RESULTS: Expressed as a percentage of whole body mass, bone mass ranged between 0.86% and 1.99%, was similar between girls and boys and correlated positively with birth weight SD (r=0.42; P<0.05) and body weight SD (r=0.35; P<0.05). No difference in bone mass percentage was found between the different types of oral feedings (fortified human milk and preterm formula) or medications studied (corticoids and diuretics). CONCLUSIONS: Whereas prenatal and postnatal weight gain determines the degree of bone mineralization of premature infants, it appears that the type of oral feeding does not affect differently the postnatal bone mineralization of premature infants, when assessed at the moment of discharge.     

Neonatal behavioural profile and crying in premature infants at term age

Aim : To analyse behavioural characteristics of infants who cried more versus those who cried less, in a sample of low-risk premature infants. Methods : Participants were 63 low-risk healthy premature infants. At term age, the Neonatal Behavioral Assessment Scale (NBAS) was administered, and a 1-d diary for crying was recorded starting on the following day. Infants were categorized into two groups: those with "high level of crying" (≥75th percentile) and those with "less crying" (<75th percentile), based on the total amount of crying time. Results : Some individual NBAS scores and "habituation" and "regulation of state" cluster scores were lower in the high-level-of-crying group. Infants in the group with a high level of crying had lower thresholds for response in the "peak of excitement", "rapidity of build-up", "irritability" and "general irritability" items. Logistic regression analysis revealed that lower "habituation" and "regulation of state" cluster scores were significantly associated with lower thresholds for crying.
Conclusion : These results suggest that neonatal behavioural characteristics, such as hyperresponsivity and poor state regulation, are associated with high levels of crying. Clinical assessments based on the NBAS may help parents elucidate their infant's level of tolerance for stimuli, and identify strategies to minimize their crying.     

Urinary hydroxyproline: relationship to growth, bone mineral content, and serum alkaline phosphatase level in premature infants

There is little information on urinary hydroxyproline (UHP) excretion in premature infants. We hypothesized that UHP excretion would positively correlate with growth in premature infants, and that there would be correlations between UHP excretion and serum alkaline phosphatase concentration as well as bone mineral content (BMC). Twenty-six premature infants (birth weight, less than 1,300 g; gestational age, less than or equal to 32 weeks) received one of four oral feedings. Seven received mother's own milk (HM), and eight received mothers own milk fortified with 0.85 g/dl of bovine whey, 90 mg/dl of Ca, and 45 mg/dl of P. Six and five infants received Similac, 20 cal/oz (SIM) and Similac Special Care, 20 cal/oz, respectively. Measurements of UHP, serum alkaline phosphatase, BMC (photon absorptiometry), and growth were made during the 1st 7 weeks of life. The lowest UHP excretion was in the HM group. For all infants, there was a significant correlation between UHP excretion (mg/day) and absolute weight (r = 0.64, p less than 0.001), as well as rate of weight gain (r = 0.50, p less than 0.01). The UHP excretion (milligrams per day) also correlated with absolute length (r = 0.41, p less than 0.01) and rate of gain in length (centimeters per week) (r = 0.70, p less than 0.001). The UHP excretion did not correlate significantly with BMC or serum alkaline phosphatase concentration. We conclude that UHP excretion is increased in the growing premature infant compared to older infants and adults and is a good marker for somatic growth in this population.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mineral balance and whole body bone mineral content in very low-birth-weight infants

Fat and mineral metabolic balance studies were performed in 25 normal very low-birth-weight infants ( 1500 g at birth) fed either pooled pasteurized human milk supplemented with calcium, phosphorus and magnesium, or a preterm formula. Calcium, phosphorus and magnesium intake were similar in both groups and averaged 100mg/kg/day, 72 mg/kg/day and 8 mg/kg/day, respectively. Calcium and phosphorus retention was higher in the subjects fed fortified human milk than in those receiving a preterm formula (65±14 and 62±9mg/kg/day versus 55±12 and 47±7mg/kg/day respectively). The difference was only significant for phosphorus. Magnesium retention was similar in the two groups and averaged 3 mg/kg/day. Fat intake and absorption was significantly higher in the preterm formula fed group than in the one fed fortified human milk (5.5±0.4 g/kg/day and 88±4% versus 4.2±1 g/kg/day, 79±6% respectively). Assessment of the whole body bone mineral content by dual energy X-ray absorptiometry was performed at 3 and 6 months of age in another group of 25 low-birth-weight infants fed either fortified human milk or a preterm formula. Whole body bone mineral content (BMCt) was low (43.3±30.8 g of hydroxyapatite) at 3 months of age (theoretical term) compared to normal full-term newborns at birth. There was no significant influence of the diet. At 6 months of age, BMCt reached 168.6±36.6g, a value similar to that of full-term newborns, with no significant difference between the two regimen groups. The deficit in the 12 subjects who had a BMCt under 30 g at 3 months of age had been corrected at age 6 months. Premature babies fed a pooled pasteurized human milk enriched with calcium, phosphorus and magnesium favored a better retention of calcium and phosphorus. However, no significant influence of the two diets studied was observed on the gain in BMCt over the first 6 months of life.     

Low bone mineral content in summer-born compared with winter-born infants.

Possible seasonal differences in newborn bone mineral content (BMC) have not been studied. Adult studies show seasonal variations with lower BMC in winter versus summer. Assuming that BMC variations may relate in part to vitamin D status, we hypothesized that newborn BMC would be lower in winter than summer. BMC of one third distal radius was measured in 55 healthy term newborns using a single beam photon absorptiometer [coefficient of variation (CV) for phantom standard 2.1%]. Infants were enrolled during summer (July-September, 1988) and winter (January-March, 1989) for a longitudinal nutrition study. Contrary to our hypothesis, there was a 12% lower BMC in summer versus winter (mean +/- SD 75.94 +/- 17.42 vs. 86.55 +/- 17.54 mg/cm, respectively; p = 0.035). The difference remained significant after controlling for possible race and gender effects (p = 0.02). We conclude that BMC is lower in summer- compared with winter-born infants. Since any seasonal effects on fetal bone are presumably related to effects through the mother, we speculate that if maternal vitamin D status influences fetal bone mineralization, the effect (possible sunshine deprivation in winter) may operate especially in early pregnancy, thus resulting in lower BMC, evident at birth in summer.     

Urinary uric acid excretion in term and premature infants

Objective : To clarify postnatal changes in urinary uric acid (UA) excretion in normal term infants and to examine the effects of prematurity or illness on the UA excretion.
Methodology : Measurements of urinary UA were performed in term and premature infants at the ages of 1 and 7 days and at 1 and 4 months, as well as at 7 months in term infants.
Results : Urinary UA levels were lowest on day 7 in term infants. The levels were highest on day 1 in premature infants and remained significantly higher compared to term babies during the first month of life. Respiratory failure requiring ventilation and oxygen supply resulted in further significant elevation of urinary UA in premature infants.
Conclusions : With the reference values obtained in the study reported here, urinary UA can now be used for the diagnosis and monitoring of inherited disorders of purine metabolism and for the assessment of oxygen radical insult to sick infants.     

Angiotensin-I-converting enzyme activity in term and premature infants.

Cord blood angiotensin-I-converting enzyme (ACE) activity was examined in 21 term and 21 premature infants. Values were significantly higher in premature infants than in term infants. Cord blood ACE activity was found to have a significant negative correlation with birth weight and gestational age. ACE activity measured from peripheral blood during the first 24 h of life was higher in premature than term infants but similar to levels in maternal and adult controls. It was not possible to predict those premature infants who would develop respiratory distress syndrome on the basis of cord blood ACE activity. However, ACE may serve as a marker for maturation of the pulmonary vascular endothelial cell.     

Symptomatic zinc deficiency in breast-fed term and premature infants

Two 3-month-old exclusively breast-fed infants, one born at full-term and the other born prematurely, developed symptomatic zinc deficiency manifested by an acrodermatitis enteropathica-like eruption. Inadequate breast milk zinc was demonstrated in both cases. A rapid clinical response followed oral zinc supplementation after which their serum zinc levels returned to normal. The infants remained asymptomatic following cessation of zinc therapy. Reports of similar cases suggest that in a group of infants breast milk does not meet their nutritional zinc requirements. Inadequate breast milk zinc is thought to result from a defect in transfer of zinc from maternal serum to breast milk.