What sign may indicate that an infant is having difficulty breathing?

Grunting sounds are a significant indicator that an infant is experiencing difficulty breathing. This sound is produced as a reflex when the infant is trying to exert pressure during exhalation to keep the air in the lungs longer, enhancing oxygen exchange. Grunting often occurs in response to low oxygen levels or respiratory distress. It is a sign that the infant is struggling to ventilate adequately and may require urgent medical assessment and intervention.

In contrast, frequent coughing can occur for various benign reasons, such as clearing secretions or mild respiratory irritation, and does not necessarily indicate distress. Smiling intermittently and feeding normally typically suggest that the infant is comfortable and not experiencing acute respiratory issues. These behaviors are more reflective of a stable condition rather than signs of respiratory distress. Therefore, grunting is the most reliable indicator of breathing difficulties in an infant.