Bone ultrasound velocity of infants born small for gestational age

Background. Quantitative ultrasound is increasingly used to assess bone status. Bone speed of sound (SOS), a biophysical property of bone, has been used to predict bone breakability. While decreased bone mineral content and delayed epiphyseal growth have been reported in small for gestational age (SGA) infants, there are no data on bone SOS in this group of infants. Objective: To test the hypothesis that SGA infants have lower bone SOS than appropriate for gestational age (AGA) infants. Methods: Bone SOS was measured within the first 96 hours of life at the right tibial midshaft in 22 singleton SGA infants. We compared these data with data obtained in 73 AGA controls(6). We used the Omnisense instrument which measures axially transmitted SOS. Infants ranged in gestational age (GA) from 25 to 42 weeks and in birth weight (BW) from 500 to 2,585 g. Statistical analyses included paired t-tests between the actual value obtained in every child and the theoretical, computed average normal value for GA, BW, or knee-sole length (KSL) based on our curves for AGA singletons. A p value <0.05 was considered significant. Results: Bone SOS measured in SGA infants was higher than the predicted computed average SOS of AGA singletons with significant differences in all of the parameters studied. Conclusions: Contrary to our hypothesis, SGA infants have higher bone SOS than AGA controls. Since bone mineral density is reported to be low in these infants, we speculate that intrauterine growth restriction may affect bone mineral density and bone protein matrix in opposite directions.