Generally through the national medical device brand certification of the Doppler fetal heart rate device will not affect the fetus, fetal heart rate device is mainly the use of ultrasound detection technology to complete the fetal heart detection, can be through the monitoring of fetal movement and fetal heart rate to reflect the condition of the fetus in the mother’s body, is mainly used for the maternal late pregnancy, prenatal and delivery of the fetus to the monitoring. Ultrasound Doppler Fetal Heart Monitor is recognized as the most accurate and widely used fetal heart monitoring method and instrument in the industry. It can be used after 15-28 weeks of pregnancy. During fetal heart rate monitoring, the fetal heart rate is regulated by the sympathetic and parasympathetic nerves, and the curve of the monitoring graph formed by the signal tracing of the instantaneous changes of the fetal heart can be used to understand the response of the fetal heart during fetal movement and contraction, in order to speculate whether there is any hypoxia of the fetus in the uterus. The radiation level of Doppler fetal heart monitor is far below the requirement of safety index, as long as it is not particularly frequent to do it. Regular checkups should be performed in the hospital during pregnancy. Fetal heart monitoring should be done once a week from the 37th week of pregnancy in normal pregnancies, or from the 28th to 30th week of pregnancy in case of co-morbidities or complications. You should pay attention to the rhythmicity of the fetal heart sound whether it is fast or slow, etc. Normal fetal heart sound is 120-160 beats/min, if the fetal heart sound is more than 160 beats/min or lasts for 100 beats/min it means that the fetus is suffering from intrauterine hypoxia, and you should go to the hospital in time for checkups and treatments.