Development of muscle ultrasound density in healthy fetuses and infants

Area of Science:

• Medical Imaging
• Developmental Biology
• Musculoskeletal System

Background:

• Muscle ultrasound density (MUD) is a valuable non-invasive metric for assessing neuromuscular integrity in pediatric and adult populations.
• Established MUD reference values for healthy fetuses and infants are currently limited, hindering developmental assessments.

Purpose of the Study:

• To establish age-related trends in MUD for major muscle groups (biceps, quadriceps, tibialis anterior, hamstrings, gluteal, calf) from prenatal development through the first year of life.
• To quantify MUD development by utilizing prenatal MUD ratios against bone density and postnatal MUD values as reference points.

Main Methods:

• Fetal MUD was measured as a ratio against bone ultrasound density to mitigate pregnancy-related signal interferences.
• Postnatal MUD values were recorded, establishing full-term prenatal MUD ratios and newborn postnatal MUD values as baseline references.
• Longitudinal measurements were taken from the second trimester of gestation through the first year of infancy.

Main Results:

• A significant increase in MUD ratio was observed during fetal development, from the second to the third trimester (median increase: 27%).
• Postnatally, MUD values showed a significant increase up to six months of age (median increase: 11%), followed by stabilization.
• Specific muscle groups exhibited distinct developmental patterns, including lower MUD in fetal hamstrings and higher MUD in pediatric gluteal muscles.

Conclusions:

• Physiologic MUD demonstrates a clear developmental trajectory, increasing throughout gestation and early infancy.
• Observed MUD trends correlate with expected maturational changes in muscle water and peptide content ratios.
• These findings provide crucial normative data for MUD, aiding in the assessment of neuromuscular development in infants and children.