In early pregnancy, the ovaries continue to produce progesterone to increase the progesterone level in the body. In the middle and late stages of pregnancy the placenta replaces the endocrine function of the ovaries, thus producing large amounts of progesterone, the value of which varies from pregnancy to pregnancy. In early pregnancy, the progesterone level is between 63.6-95.4 nmol/L, because only the ovaries secrete progesterone, and the progesterone level is relatively low. Since the placenta does not grow in early pregnancy, when the progesterone level is too low in early pregnancy, preterm miscarriage and miscarriage will easily occur.