If blood is seen during pregnancy, it is not normal. If blood is seen in early pregnancy, it is considered to be preterm miscarriage and progesterone should be checked promptly. If the progesterone level is low, you should take progesterone supplementation or diprogesterone for fetal preservation treatment in time. If blood is seen in the middle of pregnancy and there is pain in the stomach when blood is seen, it is considered to be an aura of miscarriage. If there is no stomach pain, it is considered to be a premature placenta or a borderline placenta praevia, which requires timely ultrasound examination. If blood is seen in the second trimester and the due date is reached, it is a sign that the baby is about to be born. If this happens before the due date, it is considered a sign of preterm labor and should also be promptly preserved.