In pregnant women with early intrauterine pregnancy, most of the vague abdominal pain in the first trimester is a physical discomfort caused by pregnancy and is a normal physiological phenomenon. The pain is often transient, aggravated by exertion, and relieved by lying down and resting. At this time, attention should be paid to rest. It is worth noting that if the pain is prolonged, gradually worsens, or accompanied by a little vaginal bleeding, the possibility of pre-eclampsia or miscarriage cannot be ruled out, and the diagnosis needs to be clarified immediately by rechecking blood HCG and early pregnancy ultrasound at the hospital. If a patient with no previous early intrauterine pregnancy develops pain on both sides of the lower abdomen in the first trimester and it gradually worsens, he/she should be highly alert to the possibility of ectopic pregnancy and should go to the hospital to review blood HCG and early pregnancy ultrasound to make a clear diagnosis, and if ectopic pregnancy is highly suspected, he/she should be hospitalized immediately. In addition to the two common cases mentioned above, pelvic inflammatory disease, appendicitis and enteritis can cause lower abdominal pain, all of which require differential diagnosis. In conclusion, regardless of whether it is normal or not, based on safety considerations, if lower abdominal pain occurs in the first trimester of pregnancy, it is necessary to seek medical attention in a timely manner to clarify the cause and not to wait at home to avoid ruptured ectopic pregnancy with hemorrhage and life-threatening hemorrhagic shock.