Maternal and child health represents one of the most relevant fields of interest in public health and particular attention is given to congenital pathologies. In Italy, the incidence of congenital hypothyroidism (CH) is 1:3200 live birth. CH is diagnosed at birth by neonatal thyroid screening. This allows a precocious onset of substitutive therapy which avoids severe psychomotor deficits in infants with CH. Moreover, the newborn screening program have permitted to identify transient disorders of thyroid function in newborns. These are essentially due to neonatal, maternal and environmental risk factors, especially iodine deficiency. The National Register (NR) of infants with CH was established in 1987. The aim of the NR is to provide disease surveillance and to monitor efficiency and effectiveness of neonatal screening. Furthermore, the NR represents an useful tool for developing epidemiological studies to identify possible environmental and/or familial risk factors of CH.