If spontaneous abortion occurs for 2 consecutive times, it is called recurrent spontaneous abortion. The fundamental treatment for recurrent spontaneous miscarriage should be the treatment for the cause. Due to the current level of science, not every patient with recurrent spontaneous miscarriage can find the exact cause. At present, the clinical search for the causes of recurrent spontaneous miscarriage is mostly carried out during the non-pregnant period from the following aspects: 1. basal body temperature measurement to understand the luteal function; 2. toxoplasma antibody, chlamydia and mycoplasma testing; 3. ultrasound examination to detect uterine malformations or myomas; 4. hysteroscopy or hysterosalpingography to detect uterine adhesions and other uterine pathologies; 5. karyotype of both spouses 6. Identification of the blood type of both spouses to exclude ABO blood group incompatibility; 7. Determination of thyroid function; 8. Examination of the husband’s semen for sperm deformities and excessive sperm; 9. Measurement.