The reasons for high neutrophils in pregnancy are the following: first, changes in the level of hormones in the body, because cell proliferation and division are mainly regulated by the endocrine system, after pregnancy, the level of sex hormones, estrogen and progesterone in the body will have a mild increase, which can indirectly promote the proliferation and division of neutrophils, and neutrophils will be high when pregnant. Second, the immune system function is enhanced, the collective is in a state of mild stress during pregnancy, to ensure that the body during this period of pregnancy, from external bacteria, viruses, the immune system function is enhanced, neutrophils compensatory increase. Thirdly, the redistribution of the circulating blood volume in the body leads to a tendency to shift the maternal circulating blood volume towards the fetus and a relative decrease in the maternal circulating blood volume, and neutrophils become high. Fourth, a decrease in the content of lymphocytes indirectly leads to an increase in the proportion of neutrophils.