1. Causes of Stomach Pain in Early Pregnancy Stomach pain in early pregnancy is a very common phenomenon. The main reasons include dilatation, placenta implantation and uterine contractions. These are normal physiological reactions, but they may also be caused by other problems, such as infection or miscarriage. 2. Stomach pain caused by expansion In the early stages of pregnancy, the stomach begins to expand to accommodate the growing fetus. During this process, it will cause a certain amount of pressure and stretch on the surrounding tissue, causing mild stomach pain. The pain usually does not last long and does not affect the fetus. 3. Stomach pain caused by placenta implantation when the fertilized egg is successfully implanted