Final answer:
Relaxation of the lower esophageal sphincter during pregnancy leads to gastric reflux or heartburn, as stomach acid can flow back into the esophagus. This is exacerbated by the pressure of the growing uterus on the stomach.
Step-by-step explanation:
During pregnancy, the body produces various hormones, including progesterone, which can lead to the relaxation of the lower esophageal sphincter (LES). The LES acts as a valve between the esophagus and stomach, preventing the backflow of stomach contents. When the LES relaxes, it can lead to gastric reflux or heartburn, which is a common complaint among pregnant women. This discomfort arises because the stomach acid can flow back into the esophagus, causing irritation. Additionally, the expanding uterus places pressure on the stomach, exacerbating the problem.
The hormone relaxin, which is also secreted during pregnancy, prepares the body for childbirth by increasing the elasticity of pelvic ligaments but does not directly contribute to the functioning of the LES. However, other pregnancy-related changes, like decreased peristalsis and the physical pressure from the growing uterus, can contribute to constipation and frequent urination.