Which of the following is a critical sign that indicates the need for immediate resuscitation in a newborn?

Bradycardia, which refers to an abnormally slow heart rate in a newborn, is a critical sign indicating the need for immediate resuscitation. In neonates, a healthy heart rate typically ranges from 120 to 160 beats per minute. When bradycardia occurs, it can lead to inadequate perfusion and oxygen delivery to vital organs, posing a significant threat to the newborn's life. Resuscitation efforts must be initiated quickly to restore normal heart function and ensure adequate blood circulation.

Other signs, such as the presence of meconium, hypothermia, or an overdistended abdomen, are important to monitor but do not necessarily require immediate resuscitation in the same urgent manner as bradycardia. For example, while meconium can lead to potential respiratory issues, it does not immediately compromise the newborn’s heart function. Hypothermia needs addressing, but it typically does not present an acute emergency when compared to bradycardia. An overdistended abdomen could indicate gastrointestinal issues, which may require intervention, but it is not an immediate factor that necessitates resuscitation measures.