The dark area in the uterus after 45 days of menopause may be caused by physiological reasons and poor embryonic development. 1. Physiological reasons: women with normal menstrual cycles can see the intrauterine gestational sac on ultrasound at 35 days after menopause, and the fetal buds and heart can be seen at 42 days after menopause. However, when the menstrual cycle is long or irregular, due to the late ovulation and fertilization of the eggs, resulting in 45 days of menopause or intrauterine dark area, you can follow the doctor’s instructions for temporary observation, and then review in about 1 week. 2. Embryonic dysplasia: It can also lead to intrauterine dark area in ultrasound after 45 days of menopause, and low levels of progesterone and HCG (human chorionic gonadotropin). Combined with ultrasound and laboratory tests, it can help diagnose the condition, and it is necessary to follow the doctor’s instructions to give progesterone, low molecular heparin and other fertility preservation treatments, as well as to repeat the examination on time. If there are still dark areas in the uterus after 45 days of menopause, the cause can be identified under the guidance of the doctor and treated promptly.