Stomach pain on the 30th day of the month can be considered to be related to the occurrence of gastrointestinal diseases such as gastroenteritis, late postpartum hemorrhage or pelvic inflammatory disease. 1. Gastrointestinal diseases: such as gastroenteritis, which can occur when eating unclean food and other reasons, can lead to gastrointestinal tract irritation, causing abdominal pain, nausea, vomiting and other symptoms, and can cause abdominal cramps during the attack. 2. Late postpartum hemorrhage: it is most common to develop 1-2 weeks after delivery, but there is also late onset until 2 months after delivery, which can cause abdominal pain and fever, often combined with infection and increased discharge with bad smell, and in severe cases, it can cause hemorrhagic shock, which is life-threatening. 3. Pelvic inflammatory disease: If there is endometritis, the inflammation can spread and cause pelvic inflammatory disease, at this time, there are lower abdominal pain, increased vaginal discharge and other manifestations, and the seriousness of the condition can also appear chills, high fever, headache and other symptoms. Women with post-partum abdominal pain should go to a hospital specialist in time to find out the cause of the disease, and then treat the cause and symptoms.