Pregnancy heartburn: what actually helps? 🔥 Facts: First, why it happens — progesterone relaxes the valve between your stomach and esophagus, so acid travels up more easily. Then in the third trimester the growing uterus presses your stomach upward, and there's simply nowhere for dinner to go. What tends to help: smaller meals more often instead of one big one, staying upright for a couple of hours after eating, propping your head and shoulders up at night, still water rather than fizzy, and go