Final answer:
The nurse should inform the client in the first trimester of pregnancy that the cause of indigestion and heartburn is the relaxation of the lower esophageal sphincter (LES), which allows stomach acid to flow back up into the esophagus. Lifestyle changes and medications can help manage these symptoms.
Step-by-step explanation:
During the first trimester of pregnancy, the nurse should explain to the client that the cause of indigestion and heartburn is the relaxation of the lower esophageal sphincter (LES). The increase in pregnancy hormones can cause the LES to relax, allowing stomach acid to flow back up into the esophagus and causing symptoms of indigestion and heartburn. This is a common issue during pregnancy and can be managed with lifestyle changes, such as eating smaller meals and avoiding fatty and spicy foods. Medications like antacids may also be recommended to relieve symptoms.