More than one-half of all pregnant women report symptoms of severe heartburn, particularly during their third trimester. Heartburn may occur during pregnancy because of changing hormone levels, which can affect how different foods are tolerated and how food is digested.

Pregnancy hormones can also cause the lower esophageal sphincter (the muscular valve between the stomach and esophagus) to relax, allowing acids to splash back up into the esophagus. In addition, your enlarged uterus can crowd your stomach, pushing stomach acids upward.