Your baby’s heart begins beating around 22 days after conception, about 5 weeks after your last period. At this stage, the heart is too tiny to hear even with an ultrasound. However, it may be detected as early as 4 weeks after conception as a flickering in the chest via ultrasound.
After 9 or 10 weeks of pregnancy, you might be able to hear your baby’s heartbeat. Typically your physician will use a Doppler instrument to do this. A Doppler instrument bounces sound waves off the fetal heart. These sounds return, affected by what they bounced off of, and the changes in these waves are picked up by the receiver in the Doppler. This may not be possible until around 12 weeks of pregnancy, depending on the position of your uterus and your own weight.
At around 20 weeks of pregnancy, the heartbeat can be heard without the Doppler amplification. A fetascope or stethoscope may be able to hear the heartbeat when pressed firmly on your abdomen.