Effects of prematurity, intrauterine growth status, and early dexamethasone treatment on postnatal bone mineralisation

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Abstract
AIM To examine the hypothesis that, apart from prematurity, intrauterine growth status (expressed as gestational age specific birth weight standard deviation scores), neonatal factors, and duration of dexamethasone treatment influence bone mineralisation in early infancy. METHODS In this prospective study, groups consisted of 15 preterm small for gestational age infants (SGA group) and 43 preterm appropriate for gestational age infants (AGA group). A reference group contained 17 term infants. Body size is known to affect bone mineral content (BMC), therefore postnatal bone mineralisation was measured when the study infants and controls had attained a similar body size. Bone mineral density (BMD) and BMC were determined by dual energy x ray absorptiometer of the lumbar spine (L2–L4). RESULTS Both preterm groups had significantly lower BMC and BMD than the weight matched term reference group, but no difference was found in BMC and BMD between preterm SGA and AGA infants. In stepwise regression analysis, bone area, duration of dexamethasone treatment, weight at examination, and weight gain per week were the most significant factors, explaining 54% of the variance of the BMC values. CONCLUSION In particular, weight at examination, prematurity, and possibly dexamethasone treatment, but not intrauterine growth status, affect postnatal bone mineralisation. Key messages Prematurely born SGA and AGA infants have significantly lower BMC than weight matched term AGA infants The degree of prematurity and postnatal dexamethasone treatment affect bone mineralisation, which is not affected by intrauterine growth retardation