Final answer:
The most common cause of bowel obstruction in pregnancy is the pressure from the enlarging uterus on the intestines, leading to conditions such as constipation and intestinal blockage.
Step-by-step explanation:
The most common cause of bowel obstruction in pregnancy is the pressure from the growing uterus on the intestines. During the later stages of pregnancy, constipation and other gastrointestinal complaints such as gastric reflux, often referred to as heartburn, can occur due to the upward pressure of the uterus on the stomach. Additionally, the decreased peristalsis, which might cause nausea in early pregnancy, is also believed to contribute to the constipation experienced as pregnancy progresses. The fetus exerting downward pressure on the reproductive organs can lead to frequent urination as well as may cause intestinal blockage, which can be a form of bowel obstruction. Furthermore, circulatory problems in the mother, such as clots in her legs, can also arise from the fetus's pressure on returning veins.