The fetal heart is an important basis for the survival of the fetus in the womb, generally the fetal heart appears at about 6 weeks, at first the fetal heart is fast at about 160 beats per minute, this is the original fetal heart rate, the development of the nervous system governing the fetal heart is not yet mature, with the extension of the pregnancy week, the nervous system development is mature, the fetal heart fluctuates at 110-160 beats per minute when quiet, when the fetus is moving can be accelerated to 170-180 beats per minute, or even faster. or even faster. The fetal heart rate is stable at 110-160 beats per minute during sleep and can accelerate during awakening and fetal movement, which is normal. There is a saying that the fetal heart rate below 140 beats per minute is a boy, and the fetal heart rate of a girl will be higher than that of a boy, which is not scientific! There is no difference in fetal heart rate during the fetal period. 1, the normal range of fetal heart rate: under normal circumstances after 6 weeks of pregnancy ultrasound can check the fetal heart, as long as the fetal heart range in 110-160 beats per minute, no too fast and slow or arrhythmia and stop, are normal. 2, fetal heart monitoring: after 35 weeks, fetal heart monitoring is performed to graphically present the contractions and fetal heartbeat to determine whether the fetus is developing well and to speculate whether the fetus has symptoms of hypoxia or discomfort, so the fetal heart rate is also an important basis for fetal safety and security. In this regard, it is not scientific to use the fetal heart rate to determine the sex of the fetus.