I'm just going to post a portion of what The Food and Drug Administration (FDA) wrote on its website (link will take you to the entire "consumer update" (article)):
"Fetal ultrasound imaging [2-D, 3-D & 4-D ultrasounds] provides real-time images of the fetus. Doppler fetal ultrasound heartbeat monitors are hand-held ultrasound devices that let you listen to the heartbeat of the fetus. Both are prescription devices designed to be used by trained health care professionals. They are not intended for over-the-counter (OTC) sale or use, and the FDA strongly discourages their use for creating fetal keepsake images and videos." It continues, “Proper use of ultrasound equipment pursuant to a prescription ensures that a woman will receive professional care that contributes to her health and to the health of her fetus.”
Now, what I find baffling is that this part was NOT reported. I sited two sources in a previous post that reported on the 3D/4D ultrasounds but nothing was mentioned regarding the fetal heart monitors! I found this out by going directly to the FDA website and searching 3D ultrasounds.