A prenatal ultrasound test uses high-frequency sound waves, inaudible to the human ear, that are transmitted through the abdomen via a device called a transducer. The transducer allows us to look inside the uterus at your baby. With prenatal ultrasound, the echoes are recorded and transformed into video or photographic images of your baby. The ultrasound can be used to show images of the baby, amniotic sac, placenta, and ovaries. Most prenatal ultrasound procedures are performed topically, or on the surface of the skin, using a gel as a conductive medium to aid in the image quality.