Screening for thyroid hormone levels in the first week of life is extremely important to identify infants with CH. Worldwide neonatal screening programs have been successful in decreasing childhood mental retardation related to CH by early detection and treatment. To successfully screen for CH, nurses must understand how to draw blood that will yield valid results on the metabolic screening filter paper. It is also important for the nurse to understand that thyroid levels are normally decreased in preterm infants and that regular follow-up of those low thyroid levels is crucial because levels may return to normal and eventual treatment is necessary. Early follow-up testing and treatment are essential. A thyroid scan or ultrasonography is optional and decided on by evaluating the risk-benefit ratio.