The presence of liquid dark areas in the uterus after pregnancy indicates the accumulation of blood in the uterus and is a precursor of miscarriage. Further blood tests of HCG, progesterone and estradiol should be performed, as well as thyroid function tests, to understand the causes of preterm miscarriage, and according to the results of these tests, effective fetal preservation treatment should be given and ultrasound should be performed regularly. During the period of birth control, we should also pay attention to the prohibition of intercourse and bathing, prohibit some strenuous exercises, eat less stimulating food and keep the vulva clean and hygienic. If there is fluid in the uterus caused by low progesterone, progesterone should be given for fetal preservation treatment, or intramuscular progesterone injection or oral progesterone capsules for fetal preservation treatment.