During pregnancy, blood volume increases, and the increase in plasma is relatively greater than that in red blood cells, so the blood is diluted and physiological anemia occurs. Anemia is diagnosed only when the red blood cell count is less than 3.5 million/cubic millimeter or the hemoglobin is below 10 grams/100 milliliters. Anemia may be caused by weak spleen and stomach, indigestion, lack of iron, folic acid, vitamin B12 and other hematopoietic substances, or excessive menstruation or parasitic diseases, or chronic blood loss in the digestive tract. Mild anemia has little effect on the fetus. However, severe anemia can cause fetal growth retardation and even premature birth or stillbirth. Pregnant women with severe anemia may develop anemic heart disease, and anemia also reduces the resistance of pregnant women, so other inflammations are prone to occur during pregnancy, during delivery or after delivery. Therefore, anemia should be actively prevented and treated.