Which of the following is a common sign of respiratory distress in a newborn?

A common sign of respiratory distress in a newborn is blue lips, also known as cyanosis. This occurs when there is insufficient oxygen reaching the tissues, leading to a bluish tint in areas with less blood flow, such as the lips and fingertips. In the context of respiratory distress, this indicates that the baby's respiratory system is struggling to provide enough oxygen, and the child may be experiencing hypoxemia. Cyanosis is a serious condition requiring immediate assessment and intervention.

Other signs of respiratory distress might be observable, but they do not directly indicate the critical nature of the situation as blue lips do. Rapid heart rate can be a response to various stressors, including respiratory problems, but it is not specific to respiratory distress alone. Frequent sighing and excessive sleepiness are not typical indicators of respiratory distress, as sighing may occur for various reasons and excessive sleepiness could be due to a number of factors unrelated to respiratory function.