Heartburn
This burning sensation occurs as the hormones relax the muscles in your upper stomach, allowing acids to splash into your esophagus. The contracting uterus is pushing up the stomach (and its acids) in the third trimester.
Track your weight to prevent pregnancy heartburn, avoid foods that cause heartburn (fat, spicy and citric) and eat regular, small meals. If you have a really bad case, ask your doctor about using an OTC proton-pump inhibitor (PPI) or H2 blocker to relieve heartburn.