During pregnancy, a series of physiological changes will occur in various systems and organs of the pregnant woman, mainly in the reproductive system, breasts, blood, urinary system and digestive system. 1. Reproductive system: changes in the size of the uterus, the uterus will increase in size and become softer, mainly due to hypertrophy of muscle cells. 2. Breasts: Breasts increase in size, engorgement is obvious, nipples become darker and easier to erect, areola becomes darker. 3. Blood: blood volume increases, red blood cells and white blood cells increase mildly. 4. Urinary system: because of the pressure of the enlarged uterus, the pressure in the ureter increases, plus the effect of progesterone, the smooth muscle tone of the urinary system decreases. 5. Digestive system: progesterone makes the gastric cardia sphincter relax, intestinal peristalsis is weakened, easy to constipation, rectal venous pressure increases, easy to occur hemorrhoids. These changes are normal phenomena, but if there are other discomforts during pregnancy, you should consult a doctor in time.