A: A fetal Doppler is a hand-held machine that uses sound waves to detect and amplify fetal heartbeats. Many doctors and midwives use this device during prenatal visits, allowing parents to hear the reassuring heartbeat of their growing baby. A number of parents are eager to listen to their baby in the privacy of their own home.

The Doppler machines may be purchased or rented with the approval and prescription of your physician. However, there are some challenges to using them that make me cautious to recommend them. Locating the heartbeat can be tricky. Babies are moving targets, and the location of the heartbeat can change from one moment to the next. It can be hard to find the heartbeat on a particular day, and this can cause couples anxiety.

To effectively use the fetal Doppler, you'll need to know where your uterus is as your pregnancy progresses. Your obstetrician or midwife may be willing to initially show you how to locate the fetal heartbeat. You'll need to use Doppler lotion on your belly to facilitate the process, and then direct the Doppler in several positions to try to locate the heartbeat. If you can't find it, it's most likely that your baby has moved to a position that makes the heart harder to locate.

Some couples have trouble differentiating a fetal heartbeat from a maternal one. Typically, a maternal heartbeat is between 70 and 100 beats per minute, while a fetal heartbeat is much more rapid, between 120 and 180 beats per minute.

If you couldn't find the fetal heart rate after several attempts, I recommend calling your healthcare provider and scheduling an office visit to make sure that all is fine with your pregnancy.