The fetal heartbeat can typically be detected by a Doppler as early as the fourth week of pregnancy, with the fetal circulatory system becoming more specialized around the ninth week.
The fetal heartbeat can be first detected by a Doppler device during the period of fetal development typically starting from the beginning of the fourth week of pregnancy. During this time, the primitive tube-shaped heart begins beating and is capable of electrical conduction and contraction. By approximately the ninth week, the fetal circulatory system becomes more specialized, allowing for further development and growth of the fetus from an embryo into a full-term infant.