Fetal Heart in the Early Stage of Fetal Development In early pregnancy, the fetal heart is the first organ to develop and begin to beat. Starting from the third week of pregnancy, the embryo begins to form a heart tube. Around the fourth week of pregnancy, this heart tube will differentiate into tissues such as the cardiac chamber, aorta, and veins. In the 6th week of pregnancy, the four parts of the fetal heart begin to form and begin to beat regularly. At this time, the fetal heartbeat can be heard through medical examination. Since the fetal heart is still relatively weak, the average beat per minute