Many changes during pregnancy are associated with constipation during pregnancy, such as increased progesterone, growth inhibitors, renin-angiotensin-aldosterone, decreased gastric motility and an enlarged uterus. These changes can slow intestinal peristalsis, compress the intestinal canal, relax the smooth muscles of the gastrointestinal tract and poor pelvic blood circulation, allowing stools to remain in the body for long periods of time and the water in the stool to be over-absorbed, leading to difficult bowel movements.