The correct measurement of fetal heart monitor is to tie the probe on the pregnant woman’s stomach first, and then look at the data on the monitor to judge the condition of the fetus. It is usually done after 12 weeks of pregnancy, and 34 weeks of pregnancy need to be monitored in a regular hospital. First in the pregnant woman’s stomach tied to two probes, respectively, in the top of the uterus and in the chest or back of the fetus, placed in the top of the uterus can understand the pregnant woman’s contraction response and the intensity of contractions, the other one is to detect the fetal heart rate. After successfully strapped on, the fetal heart rate and contractions will be displayed graphically on the screen of the fetal heart monitor, with 2 lines in total, the upper line indicating the fetal heart rate and the other line indicating the intrauterine pressure, which is generally around 110-160 beats/minute. The fetal heart monitor will monitor the fetal heart rate and will show the wave amplitude of the fetal heart baseline on the drawing. Fetal heart monitors use ultrasound to detect the physical condition of the fetus and will not affect the fetus.