Gastroesophageal reflux Disease(GERD) occurs when stomach contents reflux, or back up, into the esophagus during or after a meal. The lower esophageal sphincter (LES) normally opens to release gas after meals. When the LES opens, stomach contents often reflux into the esophagus and out the mouth, resulting in regurgitation, or spitting up, and vomiting.
GERD is common in healthy infants. More than half of all babies experience reflux in the first 3 months of life, but most stop spitting up between the ages of 12 to 24 months. Only a small number of infants have severe symptoms.