There are two possible causes of stomach pain in 20 weeks of pregnancy: first, some gynecological and obstetric diseases, such as preeclampsia, usually this stomach pain accompanied by vaginal bleeding, may be caused by ectopic pregnancy, which is a kind of acute and critical illness, requiring emergency medical treatment. The second category, non-gynecological diseases, such as urinary tract infections, may be accompanied by frequent urination, urinary urgency and other symptoms, as well as gastrointestinal diseases caused by, for example, acute gastroenteritis, may have eaten some unclean food led to, may also be appendicitis, usually accompanied by nausea, vomiting, fever and other manifestations. If stomach pain occurs in the 20th week of pregnancy, it is recommended to go to a regular specialized hospital to complete the relevant examinations, and give timely and effective symptomatic treatment after a clear diagnosis.