The stomach pain in the fourth month of pregnancy may be caused by physiological reasons, premature miscarriage, acute gastroenteritis and other reasons. 1. Physiological reasons: after pregnancy, along with the enlargement of the uterus, the pelvic floor and the ligaments around the uterus will have a pulling effect, and cause a slight pain in the lower abdomen, not accompanied by vaginal bleeding, this is a normal physiological phenomenon, can be relieved after appropriate rest. 2. Pre-eclampsia: it will cause paroxysmal lower abdominal pain, accompanied by a small amount of vaginal bleeding, ultrasound suggests that the development of the fetus is normal, you need to follow the doctor’s instructions to rest, and give progesterone and other drugs to protect the fetus treatment. 3. Acute gastroenteritis: can also cause pain in the stomach, can also be accompanied by nausea, vomiting, diarrhea, fever and other symptoms, mostly from improper or unclean diet history, combined with clinical manifestations and medical history can be clearly diagnosed. When four months pregnant stomach pain need to go to the hospital, and identify the cause, give positive treatment.