Is it normal for a baby over a month old to frequently hiccup? The diaphragm is a muscle closely related to breathing in the human body. If it spasms, a person will hiccup. In the first few months after birth, infants often frequently hiccup, which could be due to strong stimulation or air intake during feeding. This is quite normal. By the time they are three or four months old, the baby’s diaphragm develops more maturely and can work more effectively, reducing the frequency of hiccups accordingly.