The possible causes of stomach or waist pain one month after spontaneous abortion are caused by infection, having sex, etc. Treatment is recommended. After spontaneous abortion, infection may be caused by part of the tissue remaining, which may result in abdominal pain, back pain, irregular vaginal bleeding, purulent discharge, fever, fatigue and other symptoms, and in severe cases, it may spread to the pelvis and abdominal cavity and result in pelvic inflammatory disease, peritonitis, septicemia, infectious shock and other diseases. Carrying out sexual life can also cause abdominal pain and lumbago. In the clinic, some anti-infective drugs can be used, such as ceftriaxone, streptomycin, etc., should pay more attention to rest, regular diet, prohibit sexual life, it is recommended to go to the hospital to find out the cause of the disease, and timely treatment.