Heart beat of the fetus starts approximately six to seven weeks after ovulation. The heart starts forming by that time along with the other body parts and starts beating immediately to start the blood circulation process. Even though the requirement of circulation in the still developing fetus is minimal, the heart starts its functioning process to not only test itself but also to prepare itself for the rigors and processes that it is deemed to do. Modern heart beat detection units like fetal Doppler are well equipped to detect and time the heart beats from an early stage onwards.

During the initial stages, the heart beats are irregular and uncoordinated. It is found that the beats often fluctuate and try to maintain the sequence of the mother. As the weeks progress the number of beats increase exponentially till it reaches a peak of more than double the number of the mother’s. After this period, the heart beats of the fetus reduce and stabilize the normal pattern. The entire process is attributed to the fetal heart’s orientation towards its function and testing its own ability. The orientation pattern can also vary with different fetuses. It is also said that the gender of the fetus can be determined at this early stage by calculating the number of heart beats but this remains scientifically unproven.

The general week wise pattern of the fetal heartbeat can be generalized into six periods. The first period starts from the fifth week. The heart beat is irregular and can range between 80 to 100 beats per minute. In the second period of sixth week, the beats range from 101 to 125 BPM. The third period of seventh week will see an increase of up to 149 BPM and will further increase to around 170 BPM in the next week. The heart beats reach a peak of about 195 BPM in the fifth period or the ninth week of pregnancy. As the weeks progress, the rate of the beat gradually comes down and by the end of the twelfth week, they are more or less stabilized and range from 120 to 160 BPM.

Modern heart beat detectors like fetal Doppler can accurately stimulate the heart beat of the fetus and can detect beats as early as the sixth week. These units are available for general usage via sales or rentals. They can help parents to enjoy listening to the fetus’s heart beats, at the same time enabling them to track and monitor the progress.