American Pregnancy reports that a normal heartbeat at the gestational age of six to seven weeks is 90 to 110 beats per minute. A heartbeat is usually detected for the first time during these weeks.
American Pregnancy adds that an embryo less than 5 millimeters from the top of the head to the bottom of the buttocks may still be healthy at this stage, even if no heartbeat is detected. However, a follow-up scan within a week should detect a heartbeat. Detecting a healthy heartbeat at seven weeks is a positive sign, as the chance of the pregnancy continuing ranges from 70 to 90 percent, depending on what type of ultrasound is used.