Fetal heart monitors hear the fetal heart after at least 12 weeks. After the 6th week of a woman’s pregnancy, the fetal buds begin to form, the heart divides into the left atrium and the right ventricle in the 7th week, the fetal heart forms in the 8th week, and the heart begins to beat, and at this time the fetal heart can be monitored with a fetal heart monitor, and the fetal heart sounds are normal at 110-160 beats per minute. When listening to the fetal heart sound should pay attention to the uterine murmur, umbilical cord murmur, abdominal aortic sound to distinguish. Fetal cardiometers for home use are generally Doppler fetal cardiometers, which use ultrasound Doppler technology, and their ultrasound dose is smaller. Will not be as early as the hospital ultrasound can monitor the fetal heart, so the home fetal cardiograph generally in 12-14 weeks of pregnancy can be heard clearly, 16 weeks after the fetal heart sound is the most clear. A pregnant woman during pregnancy should pay attention to do a good job of prenatal checkups, and actively listen to the advice of a professional doctor to do a good job of comprehensive care and health care, can effectively ensure the safety of the birth. Fetal heart monitoring period is recommended to the hospital for examination, if the fetal heart abnormalities can be timely medical treatment, so as not to miss the best time for treatment.