Typically, a fetal heartbeat is detected by an ultrasound during the seventh week of pregnancy, according to the American Pregnancy Association. Detecting a heartbeat at this point is a positive sign for long-term viability of the fetus. The normal heartbeat at this age is 90 to 110 beats per minute.

In some cases, a heartbeat isn't detected by the end of seven weeks, but the fetus is still in good health. With a smaller fetus, a lack of a heartbeat is less concerning, according to the APA. However, a follow-up visit is normally scheduled within a week to recheck for a heartbeat. By week nine, the heartbeat is strong at 140 to 170 beats per minute.