Heartburn is very common during the fifth month of pregnancy due to hormonal changes and pressure from your growing baby. For safe relief, you can use over-the-counter antacids containing calcium carbonate, magnesium hydroxide, or aluminium hydroxide. Avoid antacids with sodium bicarbonate, as they can cause fluid retention. If these do not help, your doctor may suggest an H2 blocker like famotidine. To naturally reduce acidity, try eating smaller, more frequent meals, avoiding spicy or fatty foods, and staying upright for at least two hours after eating. Always consult your obstetrician before starting any new medication to ensure it is safe for your specific pregnancy.