Final answer:
Progesterone during pregnancy can cause gastric reflux, constipation, and frequent urination.
Step-by-step explanation:
During pregnancy, progesterone has several effects on the gastrointestinal (GI) system. One of the common complaints is gastric reflux or heartburn, which is caused by the upward pressure of the growing uterus on the stomach. Progesterone also decreases peristalsis, which can lead to constipation as pregnancy progresses. Additionally, the downward pressure of the uterus on the urinary bladder can result in frequent urination.