Whether the fetal heartbeat is normal or not is determined by the number of fetal heartbeats. During pregnancy, the fetal heart rate fluctuates, especially in the middle and late pregnancy, the fetal heart rate may be fast and slow. If it exceeds or is lower than this range and lasts for more than 15 seconds, it is called tachycardia and bradycardia respectively, which are fetal heart abnormalities. Clinically, this symptom is commonly caused by the following factors: 1. If the number of fetal heartbeats is lower than 120 or higher than 160, it may be caused by fetal hypoxia in the uterine cavity, such as low amniotic fluid or umbilical cord around the neck, which can cause fetal hypoxia. It is necessary to go to the hospital for ultrasound examination to clarify the cause and then give oxygen therapy; 2. It may be caused by abnormal fetal heart development, such as ventricular septal defect, ductus arteriosus, etc.