Risk factors associated with low bone mineral content in very low birth weight infants

Introduction: We report part of the findings of a study conducted to determine the correlation between bone mineral content (BMC) and biochemical bone markers in very low birth weight (VLBW) infants. Methods: This was a cross-sectional study, carried out between August 2001 and June 2004 in the neonatal intensive care unit of Hospital Universiti Kebangsaan Malaysia. Whole body BMC was measured by dual energy X-ray absorptiometry in 41 VLBW infants. Results: The mean BMC/kg body weight was 25.8 (standard deviation [SD] 11.2) g per kg. The BMC of these infants had significant negative correlation with their birth weight (r equals -0.31, p-value equals 0.048). There was no significant difference in the mean BMC between different races and gender. The infants were divided into two groups based on the course of prematurity: "non-complicated" and "complicated" groups because of the lack of "healthy reference population" data for normal BMC values in premature infants. The "non-complicated" group (30) had received ventilator assistance for less than seven days, tolerated full enteral nutrition before the age of two weeks, had no sepsis or necrotising enterocolitis and did not receive regular diuretic or steroid treatment. The cut-off level for a desirable BMC per kg in VLBW infants was obtained from a value corresponding to one SD below the mean of the "non-complicated" group, i.e., 17.4 g per kg. Eight (19.6 percent) infants had BMC less than this value. Multilinear regression analysis of demographical characteristics, maternal factors, neonatal complications and nutrition received revealed that heavier birth weight (p-value equals 0.007) and longer duration of parenteral nutrition (p-value equals 0.03) were associated with lower BMC. Conclusion: VLBW infants who required parenteral nutrition for longer periods were at higher risk to having poorer bone mineralisation.