Bone mineral density of the lumbar spine in very-low-birth-weight infants: a longitudinal study

To examine osteopenia in very low birth weight (VLBW) infants we used repeated dual-energy X-ray absorptiometry in a prospective study of lumbar spinal bone mineral density (BMD) in Japanese VLBW infants (birthweight 426-1498 g; n = 61, group 1) aged 40 weeks postconception to 3 years of age. Control subjects were Japanese infants with birthweight 1500-1999 g (group 2), 2000-2499 g (group 3), or more than 2500 g (group 4). BMD in group 1 during the early period after birth was very low, increased rapidly for 1 year, and then gradually increased until 3 years of age (r = 0.931, P < 0.0001). BMD at the age of 40 weeks postconception was 0.085 +/- 0.026, 0.132 +/- 0.039, 0.178 +/- 0.042, and 0.196 +/- 0.046 g/cm(2) in groups 1, 2, 3, and 4, respectively (P < 0.0001). However, at 1 and 2 years of age no differences were observed among the groups in BMD. Conclusion This study shows that lumbar spinal BMD in VLBW infants can normalize by the age of 2 years.