The reasons for low progesterone in pregnancy are the following: First, in terms of nutritional status, the synthesis of progesterone requires more lipids, and if women have poor absorption of substances or incomplete intake of nutrients, this will result in a relative lack of raw materials for progesterone synthesis, leading to low progesterone. Secondly, the endocrine function of women is poor, because the secretion of progesterone is regulated by negative feedback regulation, which is responsible by the hypothalamic pituitary gonadal axis, and if this axis is impaired, it may lead to a decrease in progesterone content. Thirdly, the excretion of progesterone increases, due to the inactivation of progesterone substances in the body, or the enhancement of liver excretion function, the fire extinguishing of progesterone increases, and the excretion through the kidneys increases and leads to the decrease of progesterone content in the blood, which is also a common cause. Fourth, the congenital poor physical condition of pregnant women, which is also a very common clinical decline in progesterone content.