There is a popular saying that if the heart rate of a fetus is below 140 beats per minute, it is likely to be a boy, and above 140 beats per minute, a girl. So is this correct? The fetal heart rate is regulated by sympathetic and parasympathetic nerves. The curve of the monitoring graph formed by the signal tracing of the instantaneous fetal heart changes can be used to understand the response of the fetal heart during fetal movement and contractions, in order to infer whether the fetus is hypoxic in the uterus. We all know that the normal heart rate of the fetus is between 120 beats/min and 160 beats/min. To listen to the fetal heart, you need to use a special instrument. The folklore is that if the fetal heart rate is below 140 beats per minute, the baby is a boy. In fact, the heart rate of girls is generally higher than that of boys, so it has nothing to do with the sex of the fetus for a newborn baby. The fetal heart rate is a means of predicting the well-being of the fetus, so it is important for every pregnant woman to keep a record of the fetal heart rate. At this time, pregnant women must know the normal range of fetal heart rate: 1. The normal fetal heart rate is 120~160 beats per minute; 2. The average fetal heart rate is 162 beats per minute before 20 weeks of pregnancy; 3. The average fetal heart rate is 147 beats per minute during 21~30 weeks of pregnancy; 4. The average fetal heart rate is 139 beats per minute during 31~40 weeks of pregnancy. Usually the loudest fetal heart sounds are heard on the abdominal wall of the pregnant woman above the dorsal side of the fetus, and the location of the loudest heart sounds varies due to the position of the fetal head. If the fetal heart rate is less than 120 beats per minute or more than 160 beats per minute, it means the fetal heart rate is abnormal and needs further review and monitoring. The actual fact is that it is not possible to see the sex of the fetus, but the pregnant mother should listen to the fetal heart, because it can not tell the birth of a boy or a girl, but it can reflect the development of the fetus.