I'm not meaning to be a downer here , but I visited those reccomended sites , and their info is highly misleading .
The information about the " FDA conducting numerous tests and in 30 years no adverse bio-effects from ultrasound monitoring have ever been doccumented" is true , to an extent .....what these companies are leaving out is that
#1 : these case studies were performed in regulated settings with qualified medical professionals, and most importaintly that #2 : doppler ultrasound and imaging ultrasound are two different TYPES of ultrasound . There have been no adverse effects from pulsed wave doppler ...which is the imaging doppler . The blind doppler , or handlheld ,used at the doctors is continuous wave ultrasound . The difference is this: pulsed wave ultrasound sends short mointered pulses of sound into the body. continuous wave sends a continuous stream....and most people dont know that continuous wave ultrasound is the type used in physical therapy settings to provide heat to damged tissues .
There is a reason your OBGYN doesnt keep the doppler on your tummy fro 20 minutes at a time ...because it WILL heat the amnitioc fluid . NO TESTS HAVE BEEN DONE TO CONFIRM BIOEFFECTS OF CONTINUOUS WAVE ULTRASOUND ON PREGNANCY ...because the physics of sound tell us that the fluid will heat up . Human trials will not be done because the laws of the physics of sound waves says that continuous wave ultrasound does unequivically produce heat . They have done tests on water , and soft tissue..which is how ultrasound heat therapy came to be . Continuous wave ultrasound is safe in short instances , like in the doectors office when they are confirming heart tones , but this is done efficiently and in a time frame that dodes not allow for production of heat.
These companies arent lying to you ...they are just leaving out the bits of information that aren't so good for business.
I'm not saying not to buy a doppler ...just know that you cannot monitor your baby constantly ...once or maybe twice a day , for less than 2 minutes per time . ( this includes FINDING the heartrate)
Good luck !