ObjectiveTo identify growth-related collagen and bone parameters in small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) preterm infants during the first six months post-term. In SGA preterm infants, increased growth and decreased bone acquisition, which we demonstrated previously, may be reflected by these markers. DesignObservational study within a randomized controlled trial. PatientsThirty-three SGA (weight, length or both at birth MeasurementsWeight (g), length (cm), procollagen type I N-terminal peptide (PINP; g/l), urinary helical peptide (UHP; g/mmol creatinine) and alkaline phosphatase (ALP; U/l) expressed as standard deviation scores (SDS) at term age, three and six months post-term. ResultsWeight and length gain during the first six months post-term and PINP SDS at term age, three months and six months post-term were higher in SGA compared with AGA infants. UHP SDS and ALP SDS were similar in SGA and AGA infants. PINP SDS and UHP SDS at term age and PINP SDS at three months were associated with subsequent weight and length gain until six months post-term. ConclusionsIncreased growth in SGA compared with AGA preterm infants is reflected by increased collagen type I synthesis during the first six months post-term, suggesting that PINP and UHP correspond with growth in preterm infants. An explanation for decreased bone acquisition of SGA preterm infants may be that increased collagen type I synthesis is not directly followed by increased bone mineralization.