Four weeks of pregnancy, small stomach swelling, not accompanied by other abnormal symptoms, may be pregnant body hormone level changes or the uterus gradually increase in size, etc., can be temporarily observed. If accompanied by abdominal pain, vaginal bleeding and other symptoms, do not completely exclude the possibility of preeclampsia, should seek medical attention as soon as possible. 1. Changes in hormone levels in the body after pregnancy: If the hormone levels in the body change after pregnancy, there may be a feeling of swelling in the belly when you are four weeks pregnant, which is a normal physiological phenomenon, so pay attention to rest and strengthen the nutrition during pregnancy, and there is no need for special treatment. 2. The uterus is gradually increasing: four weeks of pregnancy belongs to the early stages of pregnancy, the embryo is in the bed, the stage of development, the uterus is gradually increasing, will cause the pelvic ligaments of the pull, resulting in a feeling of bloating in the stomach, can be temporarily observed, pay attention to any other abnormal changes. 3. Pre-eclampsia: If you are four weeks pregnant with a swollen belly, accompanied by abdominal pain, vaginal bleeding and other symptoms, may be caused by pre-eclampsia, should be as soon as possible with a professional obstetrician and gynecologist examination, a clear diagnosis, and timely adoption of measures to protect the fetus. If you are four weeks pregnant with a swollen belly, it is recommended that you go to a regular hospital as soon as possible for consultation and examination to rule out the possibility of miscarriage in time.