when do you hear baby's first heartbeat
Hearing the Fetal Heartbeat. Doctors use several different methods to listen to the fetal heartbeat. About 3 weeks, one day after fertilization, when the heart first begins to beat, the sound of the little heart is too soft to hear. Very soon thereafter, they can see the motion using ultrasound technology. A doctor's stethoscope is not sensitive enough to hear the embryo's heart beating.