Low neutrophils in pregnancy is a common phenomenon, the causes of which are complex and variable, but the common causes are the following: the first reason, the ratio of blood cells in a woman’s body due to pregnancy, itself will undergo certain changes, in different periods of pregnancy, the ratio of blood cells is different is a normal physiological phenomenon. The second reason is that the estrogen and sex hormones in women’s bodies will change when they are pregnant. The third reason is that women’s bodies are in an emergency state when they are pregnant, and in order to defend themselves against external viruses and bacteria, the neutrophil count decreases while the lymphocyte ratio tends to increase at this time, which is to defend themselves against viruses and bacteria. The fourth reason is that when a woman is pregnant, her nutritional needs change significantly, which is also a reason for the decrease in neutrophils.