GERD, or gastroesophageal reflux disease, occurs when stomach contents and acid are flushed back into the esophagus, causing a host of unpleasant, even dangerous, effects. It can be caused by a failure of the esophageal sphincter, pregnancy, obesity, certain medications, a bacterial infection of the stomach, or can simply be due to unlucky genetics. Reflux that goes unmitigated can have serious medical consequences, such as stomach ulcers or a precancerous condition called Barrett’s esophagus. Heartburn. Heartburn, a dull ache or burning sensation in the center of the chest or abdomen, is one of the most common symptoms before and during the development of GERD. While occasional heartburn is normal, discomfort that goes on for several days or more should be addressed, especially if it worsens at night or is not relieved by medications.