Using ultrasound to examine muscle mass in preterm infants at term-equivalent age.

The aim of this study was to compare the skeletal muscle thickness of three different muscles and muscle groups in 44 preterm infants studied at term-equivalent age and 44 full-term controls: the biceps brachii, quadriceps femoris, and anterior tibial. The study was carried out at the Careggi University Hospital, Florence, Italy, from January 2018 to December 2019. We assumed that impaired muscle thickness in premature infants would be correlated with exposure to risk factors in the postnatal period. When the premature babies reached term-equivalent age, they were statistically significantly thinner and shorter and had a lower head circumference and lower body mass index than the full-term controls. The muscle thicknesses in the proximal and distal districts were statistically significantly smaller in prematurely born than term-born infants. The skeletal muscle thickness was related to the revised Clinical Risk Index for Babies score and days of invasive mechanical ventilation.Conclusion: Our data show that at term-equivalent age the premature babies had lower skeletal muscle mass acquisition than the full-term controls. This was particularly due to critical conditions at birth and the subsequent duration of invasive mechanical ventilation. What is Known: • The deleterious effects of prolonged mechanical ventilation on skeletal muscle function have been reported by adult intensive care studies. • Ultrasound imagines of fat and muscle thickness have been used in neonatology, as the method is safe, portable, and noninvasive. What is New: • Premature babies studied at term-equivalent age had lower muscle acquisition, but similar subcutaneous fat thickness, to full-term controls. • A high revised Clinical Risk Index for Babies score at birth, and prolonged invasive mechanical ventilation, was associated with skeletal muscle impairment.