The time when the fetal heartbeat can be heard is related to the development of the fetus and the instruments applied. Different instruments have different principles and the time when the fetal heartbeat can be heard varies; the earliest fetal heartbeat can be heard at 12 weeks of pregnancy. Generally, the baby’s heartbeat will start to appear at about 6 weeks of pregnancy, but it cannot be heard directly yet; the fetal heartbeat can be heard by ultrasound Doppler fetal heart monitor at 12 weeks of pregnancy, and after 16 weeks of pregnancy, pregnant women can hear the fetal heartbeat with home fetal heart monitor; the fetal heartbeat can be heard by ordinary stethoscope at 18-20 weeks of pregnancy; the fetal heartbeat can be checked by 4D ultrasound at 22-26 weeks of pregnancy. When listening to the fetal heartbeat, the fetal back position can be roughly judged by the fetal position, and the heart sounds are clearer when the stethoscope is placed on the fetal back, and need to be distinguished from the pregnant woman’s heart rate, intestinal sounds, uterine murmurs and so on. Although pregnant women can use a home fetal heart monitor to listen to the fetal heartbeat, but it is not recommended to listen to the fetal heartbeat frequently at home, especially for pregnant women who are usually nervous.