If you have pain in the small of the abdomen in the third trimester, you should pay attention to the possibility of pre-miscarriage and need to go to the obstetrics and gynecology department for further examination in time. In addition, it is important to suspect the possibility of appendicitis, which usually starts with pain around the umbilicus and gradually shifts to the right lower abdomen, usually for 3 or 5 hours, or even longer. There is obvious pressure pain and rebound pain leading to the right lower abdomen, and the pain is relatively fixed. There is also the possibility of pelvic inflammatory disease, or the possibility of acute gastroenteritis if you have eaten something bad, or if your abdomen is cold, acute gastroenteritis is usually accompanied by diarrhea, vomiting, you can pay attention to the diet by paying attention to rest, observe and see if the abdominal pain is relieved, no further treatment is needed, if the abdominal pain continues to worsen, further relevant examination is needed.