Impact of intra- and extrauterine growth on bone mineral density and content in the neonatal period of very-low-birth-weight infants

Background: Very-low-birthweight infants (VLBWIs) are at high risk for suboptimal bone mineral density (BMD) and bone mineral content (BMC). Small-for-gestational-age (SGA) status also causes reduced bone mineralization in full-term infants. However, the impact of intrauterine and postnatal extrauterine growth on BMD and BMC in VLBWIs is inconclusive. Methods: We retrospectively investigated n = 68 VLBWIs, comprising 45 appropriate-for-gestational-age (AGA) and 23 SGA infants who underwent lumbar spine dual-energy X-ray absorptiometry at term-equivalent age. Results: BMD and BMC did not differ between AGA and SGA VLBWIs. Subgroup analyses of infants with birthweight < 1000 g vs 1000–1500 g, and GA < 27 weeks vs ≥27 weeks also showed no differences in BMD and BMC between AGA and SGA infants. In contrast, infants with extrauterine growth restriction (EUGR) showed significantly lower values than those without (BMD: 0.124 ± 0.023 vs 0.141 ± 0.032 g/cm2, P = 0.02; BMC: 0.80 ± 0.26 vs 0.94 ± 0.23 g, P = 0.04). There were no differences between AGA and SGA infants with EUGR. However, in the AGA cohort, infants with EUGR showed significantly lower values than those without (BMD: 0.121 ± 0.022; 0.141 ± 0.03 g/cm2, P = 0.02; BMC: 0.73 ± 0.23 vs 0.94 ± 0.23 g, P = 0.005). Multiple regression analyses showed GA, weight and head circumference at birth, and weight percentile at term correlated with term BMD. Conversely, only weight percentile at term significantly correlated with term BMC. Conclusion: EUGR, rather than IUGR, is a risk factor for reduced BMD and BMC in the neonatal period in VLBWIs.