With my first pregnancy, I rented a fetal doppler so that i could hear the baby's heartbeat at home, between doctor visits. After some searching around, I discovered that for less than what i would have to pay to rent, i could actually OWN my own doppler, like they use in the doctor's office. So for my second pregnancy, we bought one!
The Contec is a small handheld doppler. There is a lighted display that shows the baby's heartrate in numerical value. Large numbers, easy to read. This particular unit came with the gel needed for use (described below). THIS IS NOT AN ULTRASOUND MACHINE OR A SONOGRAM MACHINE. This provides you with audio ONLY of a fetal heartbeat.
I have found this unit to be sensitive enough to detect the baby's heartbeat at approximately 11 weeks gestation, although according to instructions, that is a little early. Typically the heartbeat is heard around 12 weeks. The way it works: there is a small wand attachment that looks like a microphone. You apply a small amount of gel to the wand and place on the abdomen. The unit emits ultrasound waves that are then "bounced back" and give a representation of the baby's heartbeat. Especially in early pregnancy, you will probably have to "look" around quite a bit for the fetus, just by moving the wand around the abdomen. Just think of how they do it in the doctor's office, it is the same process.
Since my husband wasn't always available to go to the doctors appointments with me, he loved being able to hear the baby at home and be a part of the pregnancy experience. Well worth the money!