The fast heart rate in the 6th month of pregnancy may be caused by fetal hypoxia, or it may be caused by fetal activity, fast heart rate of pregnant women and other reasons. 1. Fetal hypoxia: the lack of blood flow in June pregnancy due to maternal blood flow, obstacles to the transport of oxygen between the pregnant woman and the fetus, and fetal anomalies can lead to intrauterine hypoxia, intrauterine hypoxia in the early stages of the fetus can be manifested as a fast fetal heart rate, and when hypoxia is aggravated, the fetal heart rate slows down. 2. Fetal activity: Fetal heart rate increases when the fetus moves, which is a normal physiological phenomenon. This is a normal physiological phenomenon. It is a transient reaction, and the fetal heart rate can drop by itself when the fetal movement is calm. 3. Rapid heart rate of pregnant women: pregnant women because of fever, mental stress, irritability, pregnant women taking drugs and other reasons can lead to pregnant women’s heart rate increase, reflex caused by the rapid heart rate of the fetus. The fast heart rate in 6 months of pregnancy timely consultation, under the guidance of the doctor to identify the causes, give appropriate treatment.