An ultrasound is a tool that uses sound waves to "see" structures inside the body. The sound waves bounce off muscles, organs and tissues in your body, providing the ultrasound technician with information about how big structures are, like your uterus or your baby, or the composition of those structures. This is why an ultrasound can show your baby's heartbeat and growth.
The first ultrasound normally occurs when you are around eight weeks pregnant to confirm that your pregnancy is healthy and to monitor your baby's heartbeat.
Early ultrasounds are performed inside your body, or transvaginally. Later ultrasounds are performed from the outside through your stomach.
Since ultrasounds use only sound waves to examine your baby, there are very few risks associated with them. You will have a chance to discuss any concerns with the ultrasound technician before the test is performed.