Postnatal "speed of sound" decline in preterm infants: an exploratory study

"Speed of sound" (SOS), measured by quantitative ultrasound, is a noninvasive method of assessing bone status. At expected term and 1, 2, and 3 months of corrected age, bone status and body fat mass were assessed by quantitative ultrasound and by an air-displacement system in 53 preterm infants to explore whether longitudinal changes in bone health were influenced by body fat mass. SOS decreased within the first month of corrected age. Body fat mass increased significantly. No correlation between SOS and body fat mass was found. SOS was not influenced by changes in body fat mass. The decline in SOS may be ascribed to bone structure factors.