If the stomach pain is a little hidden in the third month of pregnancy, if it is milder and appears occasionally, consider that it may be related to the enlarged uterus, if the pain is obvious and continues to increase, some pathological factors should be considered, which may be seen in the following reasons: a. Physiological phenomena: 1. The uterus increases: the third month of pregnancy belongs to the early pregnancy period, when the uterus gradually increases and enters the abdominal cavity from the pelvis. The enlarged uterus will pull the pelvic ligaments, resulting in the symptoms of hidden pain in the stomach. It is recommended to pay attention to rest and not to do heavy physical labor or strenuous sports. 2. Pseudocontractions: If there is a symptom of tightening of the belly when the vague pain in the stomach is present, consider an occasional contraction. The fetus is prone to transient hypoxia during contractions, which may affect the normal development period of the fetus and may be transformed into true contractions, it is recommended to go to the hospital for examination in time. Second, pathological phenomena: 1. Pre-eclampsia: abdominal pain caused by pre-eclampsia, which is paroxysmal abdominal pain with vaginal bleeding, is recommended to go to the hospital for treatment in time; 2. Ectopic pregnancy: ectopic pregnancy in some special areas, such as ectopic pregnancy in the uterine horn or ectopic pregnancy in the interstitial part of the fallopian tube, where the uterine embryo ruptures relatively late and may appear in the third month of pregnancy. Therefore, if no ultrasound examination has been done before to confirm intrauterine pregnancy, abdominal pain at 3 months needs to be confirmed by ultrasound; 3. Gynecological diseases: such as tumor, cancer, inflammation, etc., can cause symptoms of abdominal pain, and it is recommended to go to the hospital for differentiated treatment. It is recommended that pregnant women with abdominal pain symptoms or accompanied by other discomfort should go to the hospital immediately and be treated under the guidance of a doctor to avoid delaying the condition.