When using a stethoscope to listen to the fetal heart, it is usually necessary to place the stethoscope against the abdominal wall of the pregnant woman in order to get an idea of the fetal heart. Usually, the stethoscope can be used to monitor the fetal heart at 18-20 weeks of pregnancy. When monitoring the fetal heart, you can let the pregnant woman lie flat, and then put the stethoscope on the abdominal wall of the pregnant woman, the specific position is mainly concentrated in the middle of the navel and the left and right sides, so that you can hear the fetal heart sound more clearly. Generally speaking, the normal fetal heart sound is two-tone, about 110-160 beats / min, sounds similar to the clock ticking. However, it is important to note that it is best to use the stethoscope in direct contact with the skin, and to maintain a quiet environment, trying to exclude external disturbing sounds, so as not to affect the monitoring results.