 [ Symptoms ] what is heartburn [ Disease ] despite its name heartburn has nothing to do with the heart some of the symptoms however are similar to those of a heart attack or heart disease  heartburn is an irritation of the esophagus that is caused by stomach acid and is a common part of pregnancy with gravity is help a muscular valve called the lower esophageal sphincter or les keeps stomach acid in the stomach the les is located where the esophagus meets the stomach    below the rib cage and slightly left of center normally it opens to allow food into the stomach or to permit belching then it closes again but if the les opens too often or does not close tight enough stomach acid can reflux or seep back into the esophagus and cause a burning sensation occasional heartburn is not dangerous but chronic heartburn can indicate serious problems such as gastritis and can develop into gastroesophageal reflux disease or gerd heartburn is a daily occurrence for 10 of americans and 50 of pregnant women it is an occasional nuisance for another 30 of the population