The fast heartbeat of pregnancy is mainly caused by the heart to adapt to the changes in the body of pregnancy capacity increase, blood volume increased. 1. Heart changes: the uterus of pregnancy increases the diaphragm elevation, resulting in the heart to the left upper shift, blood flow increases and the speed of blood flow accelerated, in the process of pregnancy the heart in order to better blood supply to the organs of the body, the heart rate gradually accelerated in order to meet the organs and the fetus’s blood supply, the 32-34 weeks of gestation is the largest amount of circulating blood in the period of gestation. 2. Increase in blood volume: The blood volume in the pregnant woman’s body increases significantly due to the presence of the fetus in the heart. In order to adapt to such changes, the heart increases the heart rate to prevent a large amount of blood from accumulating in the heart and veins, and to prevent the production of bruises, etc. If you feel unwell, you should go to the hospital for a clear diagnosis. If there is any discomfort, you should go to the hospital for a clear diagnosis and be guided by the doctor to use the medication so as to avoid any adverse effects on your body.