Infant’s grunting may be related to tight clothing, wanting to urinate and defecate, gastrointestinal dysfunction, and sleep transition. 1. Clothes are too tight: If an infant’s clothes are too tight, resulting in the limbs not being able to stretch out, making the body uncomfortable, he or she will grunt and make efforts to stretch out the limbs. 2. Wanting to defecate: Some infants will grunt and make efforts to promote defecation when they want to defecate or urinate. 3. Gastrointestinal dysfunction: Infants’ gastrointestinal function is relatively fragile, and the digestive system is immature, so if the cold causes abdominal discomfort and gastrointestinal dysfunction, infants may grunt and make a lot of noise. 4. Sleep transition: Infants have a short sleep cycle, and during sleep transition, they may grunt and grunt vigorously, similar to rolling over, stretching and other movements. Parents are advised to keep an eye on their infant’s physical condition when the infant is grunting and making a lot of effort, and to go to the hospital promptly if they feel unwell.