Once the milk cries, there may be mouth ulcers, insufficient breast milk, gastrointestinal dysfunction, etc.. 1. Mouth ulcers: if the baby has mouth ulcers, when breastfeeding to stimulate the ulcer site, obvious pain, there will be crying and refusing to breastfeed, etc., you can check the oral cavity to confirm the diagnosis. 2. Insufficient breastmilk: If the mother’s breastmilk secretion is low, the baby sucks with great effort, and the hunger is not satisfied, there will also be crying while breastfeeding. 3. Gastrointestinal dysfunction: If the baby has gastrointestinal dysfunction due to cold and other reasons, indigestion, bloating, etc., breastfeeding may aggravate the symptoms of abdominal distension, and there will also be crying. As soon as breastfeeding cries, you can first take your baby to the hospital to find out the cause and then treat it.