The fetal heart sounds are binaural and fast, 110-160 beats per minute in normal. The fetal heart rate of 170 beats per minute in the third month of pregnancy is faster than the normal heart rate, but most of the cases are normal. The faster fetal heart rate may be a result of maternal stress, exertion or fetal activity, and the heart rate will speed up when the fetus is calm and sleepy. The fetal heart rate is affected by the duration of pregnancy, umbilical cord condition, amniotic fluid condition and placenta condition. If the fetal heart rate is longer than 160 beats/min, it is important to consider whether the fetus has tachycardia or even intrauterine distress. In the middle and late stages of pregnancy, if the fetal heart rate increases, it may be due to the lack of oxygen in the uterine cavity and requires oxygen therapy under the guidance of a doctor.