出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/07/08 23:02:54」(JST)
Fetal Dopplers or Baby Heartbeat Monitors
Originally intended for use by health care professionals, despite this, Fetal Doppler devices have become extremely popular for personal use.
The fetal Doppler is a handheld ultrasound baby heartbeat monitor that your caregiver can use to find your baby's heartbeat. She'll cover it with ultrasound gel and move it around on your belly until she finds a spot where the heartbeat can be detected. The Doppler sends and receives sound waves that bounce off your baby's heart. In this way the fetal Doppler makes your baby's heartbeats loud enough for you to hear.
These pocket-sized, battery-operated devices are easy to find for rent or sale online. They usually have a handset with controls, a built-in speaker, and a transducer probe that you cover with ultrasound gel and hold against your lower abdomen.
The probe sends out high-frequency sound waves that pass through your skin and tissue and into your baby. When the waves encounter movement, such as your baby's heart beating, they bounce back to the device. The device then translates the movement into sound, which the machine amplifies so you can hear it.
Yes, you can rent or buy a Doppler for home use. However, many times renting is more expensive compared to buying your own.
Many women say that the beating of their baby's tiny heart sounds like the thunder of galloping horses. Hearing it for the first time can be very moving. The heart rate of a healthy baby in the womb ranges from about 120 to 160 beats per minute. A heartbeat that's much faster or slower than that may signal a heart problem.
Let your doctor or midwife know you're thinking about buying or renting a Doppler.
Dopplers range from about $50 to $500 to buy, and the more expensive models are generally similar to the less expensive ones in terms of features and reliability. You can rent them for about $15 to $50 per month or you can purchase one for under $40.
Check that the Doppler conforms to FDA safety standards and, if you're buying it, that it comes with a warranty.
Make sure the Doppler comes with instructions for use and guidance on how to interpret what you hear.
You'll need gel formulated for use with ultrasound. Other gels or oils can cause excess static and may damage the Doppler probe.
Ignore any claims from a Doppler manufacturer that its device can pick up a heartbeat at 8 or 9 weeks. Experts recommend waiting until you're at least 13 weeks pregnant to try to find your baby's heartbeat. Avoid using the Doppler for more than a few minutes a day. While ultrasound is generally considered safe, researchers continue to study the possible risks of repeated and prolonged exposure.
The baby's heart starts to beat at around 6 weeks. You may be able to hear – and see – your baby's heart beat for the first time when you're about 8 weeks pregnant if you have an early ultrasound exam.
Otherwise, you'll probably first hear it with a fetal Doppler at a regular prenatal care visit. Your caregiver may be able to find it with the Doppler as early as 10 weeks, but it's more common to hear it at 12 weeks. How early the sound can be picked up depends on your baby's position in your uterus, your weight, and the accuracy of your due date.
Checking your baby's heartbeat will become a regular part of every prenatal visit. Here are a few other things you may want to know:
Many women say that the beating of their baby's tiny heart sounds like the thunder of galloping horses. Hearing it for the first time can be very moving. The heart rate of a healthy baby in the womb ranges from about 120 to 160 beats per minute. A heartbeat that's much faster or slower than that may signal a heart problem.
Invented in 1958 by Dr. Edward H. Hon,[1] a Fetal Doppler Monitors or Baby Heartbeat Monitors is a hand-held ultrasound transducer used to detect the fetal heartbeat for prenatal care. It uses the Doppler effect to provide an audible simulation of the heart beat. Some models also display the heart rate in beats per minute (BPM). Use of this monitor is sometimes known as Doppler auscultation. Doppler fetal monitors are commonly referred to simply as "Dopplers" or "Fetal Dopplers".
Doppler fetal monitors provide information about the fetus similar to that provided by a fetal stethoscope. One advantage of the Doppler fetal monitor over a (purely acoustic) fetal stethoscope is the electronic audio output, which allows people other than the user to hear the heartbeat. One disadvantage is the greater complexity and cost and the lower reliability of an electronic device.[citation needed]
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Recording From a Fetal Doppler Monitor
Recording from a consumer grade fetal doppler monitor of a ~16 week fetus.
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Originally intended for use by health care professionals, this device is becoming popular for personal use.
Starting at week 5 the fetal heart rate accelerates by 3.3 bpm per day for the next month.
The fetal heart begins to beat at approximately the same rate as the mother's, which is typically 80 to 85 bpm. The approximate fetal heart rate for weeks 5 to 9 (assuming a starting rate of 80):
At this point, the fetal heart rate begins to decrease, and generally falls within the range of 120 to 160 bpm by week 12.[2]
Dopplers for home or hospital use differ in the following ways:
A major advantage of being able to record and share the recording is that it can be emailed to a healthcare professional to be checked if there are any concerns about whether or not it is the baby's heart rate and whether or not is normal. Typically, they work from about 12 weeks.[citation needed]
The use of the word "Sonicaid" for Doppler fetal monitors comes from the products of the UK company Sonicaid Ltd. Sonicaid products included the D205/206 portable fetal Dopplers and FM2/3/4 series of fetal monitors. The company was acquired by Oxford Instruments in 1987 to form Oxford Sonicaid.
It was recently demonstrated that continuous Doppler enables the auscultation of valvular movements and blood flow sounds that are undetected during cardiac examination with a stethoscope in adults. The Doppler auscultation presented a sensitivity of 84% for the detection of aortic regurgitations while classic stethoscope auscultation presented a sensitivity of 58%. Moreover, Doppler auscultation was superior in the detection of impaired ventricular relaxation Since the physics of Doppler auscultation and classic auscultation are different, it has been suggested that both methods could complement each other.[4][5]
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