Which of the following is a sign of dehydration in a newborn?

Lethargy and fewer wet diapers are significant indicators of dehydration in a newborn. Newborns have a limited ability to conserve water, and when they become dehydrated, they may exhibit decreased energy levels, leading to lethargy. The production of fewer wet diapers is a critical sign, as these infants should typically have a specific number of wet diapers each day, which indicates proper hydration and kidney function. Dehydration can also cause other symptoms like dry skin, mucous membranes, and changes in urine concentration, but lethargy paired with reduced wet diapers is a clear and notable sign that warrants further evaluation and intervention.

In contrast, increased appetite, bright eyes with clear skin, and increased feeding frequency are not indicative of dehydration. A newborn with a healthy hydration status typically feeds regularly, exhibits energy, and has moist mucous membranes and skin with normal elasticity. These contrasting signs illustrate the importance of monitoring hydration status closely in newborns, as their needs can change rapidly.