Excessive platelets 400×10^9/L in pregnant women may be caused by physiological reasons or pathological reasons such as iron deficiency anemia and primary thrombocythemia. 1. Physiological reasons: pregnant women due to hormonal changes in the body, platelets may be elevated, there may be platelets 400 × 10 ^ 9 / L, which is usually normal, do not need to do special treatment. 2. Pathologic causes (1) Iron deficiency anemia: Iron deficiency anemia can lead to a weakening of the maturation inhibition of megakaryocytes, resulting in an increase in megakaryocytes, leading to an increase in platelets released from the bone marrow into the peripheral blood, which can lead to peripheral blood platelet hypercapnia, and values of up to 400×10^9/l can occur. (2) Primary thrombocythemia: this disease is a chronic myeloproliferative disease characterized by the continuous proliferation of bone marrow megakaryocytes, increased platelet count and abnormal function, and elevated platelet count is a typical symptom, which may be manifested as a platelet count of 400 x 10^9/L. Pregnant women with high platelet counts of 400×10^9/L are advised to go to a regular hospital for further examination, to clarify the cause and treatment in time, so as to avoid affecting the pregnant woman and the fetus.