The vague pain in the abdomen on the 45th day of pregnancy may be a normal bodily reaction, or it may be due to the occurrence of a prior miscarriage, ectopic pregnancy or other factors. 1. Normal body reaction: During pregnancy, due to the strong secretion of hormones in the body, it may cause some stimulation to the abdominal tissues, so this symptom will appear, and it is generally more normal. 2. Pre-eclampsia: If the development of the fetus is unstable during pregnancy and pre-eclampsia occurs, it may cause vague pain in the abdomen and bleeding and other reactions. 3. Ectopic pregnancy: if there is an ectopic pregnancy, the fetal development process on the abdominal cavity caused by extrusion, may lead to capillary rupture bleeding, but also the symptoms of hidden pain in the abdomen. 4. Other factors: such as gastroenteritis, trauma and other factors may also be caused by abdominal pain. If the pain symptoms are more obvious, it is recommended to go to the hospital in time for examination, to clarify the cause of the disease, and then follow the doctor’s instructions to deal with the treatment.