Low progesterone but normal HCG secretion usually indicates good embryonic activity and normal development, but luteal insufficiency cannot be ruled out. Therefore, attention should be paid to this situation and regular testing should be done to ensure healthy fetal development. Common causes and treatments 1. Normal situation: During the whole pregnancy, progesterone is secreted in pulses, and the hormone level is not constant during the day, usually the progesterone content is higher in the early morning, while the secretion is slightly lower in the afternoon, evening and night. If the HCG doubling is normal and there is no vaginal bleeding or abdominal pain, the simple transient reduction of progesterone is not a problem and there is no need to worry too much; 2. Abnormal situation: If the progesterone is reduced and the blood HCG doubling is normal, but a small amount of vaginal bleeding and persistent abdominal pain are found to occur, it is considered to be a preterm abortion caused by abnormal luteal function and low progesterone. It is recommended to go to hospital for fetal preservation treatment and supplement progesterone under the guidance of doctor, either orally or intramuscularly, and pay attention to the development of fetal bud and fetal heart according to ultrasound to assess the embryonic condition. The pregnant woman should pay attention to the regular maternity checkups and seek medical treatment in time to find the problem, not to diagnose blindly by themselves, and not to use drugs indiscriminately to avoid irreversible consequences.