The causes of hiccups when a four-month-old baby laughs mainly include the following situations: first, caused by the baby inhaling air when laughing, if the four-month-old baby enters a large amount of air into the stomach when laughing, this situation will cause hiccups. You can timely pat the back, so that the baby’s stomach gas smooth after the natural hiccups will no longer. Secondly, due to the baby suffers from indigestion caused by the symptoms, if the baby’s body in April indigestion, this situation will also cause hiccups when laughing, often accompanied by bad breath, stool in the indigestible food or milk petals and other accompanying symptoms.