Your baby's heartbeat is one of the first things your doctor will look for on an ultrasound, a test that uses sound waves to give off visual images of your baby and placenta as well as your uterus and other pelvic organs.
Your baby's heart starts beating about 22 days after she's conceived, but the earliest you'd be able to spot it onscreen is five weeks after your last period (although many moms-to-be don't see the doctor until they're a bit farther along in their pregnancies). Your baby is so teeny that she may be hard to ID during your first ultrasound, but the heartbeat will look like a very fast flicker. If you don't see one at your first visit, don't panic. It could still be too early, especially if your doctor miscalculated how far along you are (which can happen if you have longer-than-normal menstrual cycles).