Progesterone is a progesterone hormone. When progesterone is low, it may cause abnormal menstruation, infertility and pregnancy miscarriage. When you are not pregnant, low progesterone may cause abnormal menstruation, irregular menstruation, prolonged absence of menstruation, scanty menstruation, incomplete menstruation, irregular vaginal bleeding, etc. It may also affect pregnancy and cause infertility. After pregnancy, low progesterone mainly affects the early stages of pregnancy and may cause miscarriage, poor embryo development and embryonic abortion. When low progesterone is found, progesterone capsules or progesterone injection should be taken under the guidance of a doctor for treatment.