Low progesterone during pregnancy may cause symptoms such as vaginal bleeding, lower abdominal pain, and can even lead to the onset of preterm miscarriage. Non-pregnancy if low progesterone can trigger menstrual disorders, need to be analyzed specifically. 1. During pregnancy: low progesterone during pregnancy will lead to uterine contractions and a small amount of the embryo’s sac peeling off from the uterine wall, which will cause lower abdominal pain and vaginal bleeding, and in severe cases, preeclampsia or even miscarriage will occur. 2. Non-pregnancy: Low progesterone in non-pregnancy will cause luteal insufficiency, which will lead to menstrual disorders and a series of symptoms such as irregular menstrual cycle, prolonged menstrual period, dribbling of menstruation, and bleeding in non-menstrual period. If a woman has low progesterone, she should go to the hospital for examination to clarify the cause of the disease and be treated under the guidance of the doctor.