First, to date, no data are available on the thyroid volume of full-term newborns in Italy, making it essential to conduct studies to establish reference values for normality. This allows these values to be correlated with maternal and fetal variability, providing a scientific basis for better understanding thyroid development in the first days of life. Thyroid ultrasound is useful for supplementing newborn screening for congenital hypothyroidism, helping to identify early abnormalities. Furthermore, thyroid volume is a sensitive indicator of iodine intake, essential for assessing the population's iodine nutritional status. It is equally valuable for studying and monitoring the effects of maternal and environmental factors, for which thyroid volume itself serves as a marker. Having normal values allows for a more precise comparison and contextualization of data from children with pathologies, who undergo ultrasound for pathological screening. In summary, these regulatory references improve the diagnosis, prevention, and management of neonatal thyroid dysfunction, contributing to a more informed public health.