Spit-up is most common in the earliest months of a child's life and typically occurs less often as a child nears 1 year and beyond. (Spitting up usually begins before a child turns 6 months old if it is going to appear.)

Why did my baby suddenly start spitting up?

What causes spitting up? Spitting up is common in healthy babies. During their first three months, about half of all babies experience their stomach contents coming back up into the esophagus, a condition known as gastroesophageal reflux, infant reflux or infant acid reflux.

What age does reflux peak in babies?

Infants are more prone to acid reflux because their LES may be weak or underdeveloped. In fact, it's estimated that more than half of all infants experience acid reflux to some degree. The condition usually peaks at age 4 months and goes away on its own between 12 and 18 months of age.