As noted above, sex hormones are activated and contribute to an increase in the volume of the muscle fibers of the uterus. It is expanding. If a woman has high sensitivity, then she may feel a pulling pain in the lower abdomen. This is normal. The process of embryo implantation can also be accompanied by short-term pain. If the pain is severe, this is an alarming sign that requires immediate medical attention and examination, especially if a woman suggests the possibility of pregnancy.