What is the primary purpose of using UV lights on "sun-tanning" babies?

The primary purpose of using UV lights on "sun-tanning" babies relates specifically to the treatment of elevated bilirubin levels in the blood, a condition known as neonatal jaundice. When babies are born, particularly premature infants, they may have difficulty processing bilirubin, a byproduct of the breakdown of red blood cells. This can lead to jaundice, characterized by yellowing of the skin and eyes.

UV light therapy is an effective method for reducing bilirubin levels. The light alters the bilirubin molecules in the skin into forms that can be more easily excreted by the baby's liver. This phototherapy process helps to prevent the potential complications associated with high bilirubin levels, including kernicterus, a severe form of brain damage.

Other options do not reflect the primary use of UV light therapy in this context. Enhancing skin pigmentation is not a therapeutic goal and does not directly address the medical condition present in infants. Stimulating red blood cell production and promoting weight gain are also not relevant uses in the management of jaundice. Therefore, the use of UV lights is specifically aimed at effectively managing bilirubin levels, making it the correct answer.