Progesterone is a progesterone secreted by the ovaries and is a hormone necessary for the maintenance of pregnancy, with different blood levels at different times during pregnancy. In general, the level of estrogen in the mother’s blood is also referred to during pregnancy. When estrogen levels are stable as well as when the fetus is growing and developing well, there is no need to worry too much when progesterone levels are slightly low. However, if progesterone is significantly low, it may often have certain effects on the fetus: 1. developmental delay: progesterone has the function of promoting the embryo and fetal intrauterine growth and development, and the development of the embryo will be affected after low progesterone, which will make the development of the fetus lower than normal and even cause fetal arrest; 2. miscarriage: high or low progesterone cannot be used as the main indicator to judge the survival of the embryo. However, if there are factors such as luteal insufficiency, low progesterone may lead to miscarriage, which needs to be treated with fetal preservation as soon as possible. When progesterone is below 5ng/ml, the effect of fertility preservation treatment is not good. It is mainly because progesterone can make the glands in the mucous membrane of the uterus grow, the uterus is filled with blood and the lining becomes thicker, so that the fetus can grow and develop safely. When progesterone is too low, it cannot achieve the effect of uterine smooth muscle relaxation, and insufficient estrogen causes the endometrium to become thin, which is not conducive to the embryo’s implantation and development, so it may lead to the occurrence of preterm miscarriage; 3. Preterm labor: progesterone can reduce the excitability and sensitivity of the uterus during pregnancy, and if progesterone is low, it may not be able to inhibit the excitability of the uterus, thus leading to preterm labor and causing certain effects on the fetus. Patients with a history of pre-eclampsia and recurrent miscarriage can take progesterone supplements for prophylactic fetal preservation. In daily life, pregnant women should pay attention to rest on time, avoid staying up late, pay attention to avoid strenuous exercise, eat a reasonable diet to ensure balanced nutrition, and maintain emotional stability and regular checkups at the hospital.