Growth and bone mineralization in small-for-gestational-age preterm infants.

Background: Preterm infants are at risk for metabolic bone disease and suboptimal growth. This study examined the hypothesis that, apart from prematurity, intrauterine growth status (expressed as gestational age-specific birthweight standard deviation score) influences bone mineralization and body composition in early infancy.

Methods: In this retrospective study, the groups consisted of preterm small-for-gestational-age (SGA) infants (n = 18; SGA group) and preterm appropriate-for-gestational-age (AGA) infants (n = 24; AGA group). Postnatal bone mineralization was measured at term-adjusted age (postmenstrual age, 37-42 weeks). Bone mineral content (BMC) and body composition were determined on dual-energy X-ray absorptiometry of the whole body.

Results: BMC and lean mass were significantly lower in the SGA group than in the AGA group at term-adjusted age (37-42 weeks postmenstrual age). Stepwise regression analysis identified weight at examination as the most significant factor, accounting for 51% of the variance in BMC.

Conclusions: Bodyweight at term-adjusted age, rather than intrauterine growth, may affect postnatal bone mineralization in preterm low-birthweight infants. Therefore, promoting an increase in body size might increase postnatal bone mineralization in preterm SGA infants.