just thought I'd add part of an article on u/sounds cited recently on this list.
From: www.mayo.edu/ultrasound/news
> When ultrasound hits bone, Fatemi says, it can produce vibrations in a fetus's
> sensitive hearing structure. A similar phenomenon occurs when you tap your
> finger close to your ear. The sound seems loud to you because of the
> vibrations produced in your ear, Fatemi says, but no one else in the room
> would be able to hear the sound. Based on his experiments, Fatemi concluded
> that ultrasound vibrations sound like the high tones of a piano, at about the
> same volume as an approaching subway train.
Sounds like good fun eh??
Sue
I had a chat with my hubby about this issue as he is a sonographer.
On the accuracy of the image representations they are actually very accurate. Yes the image is a computer composite of ultrasonic images but the information received is accurately calculated into a composite picture - not an interpretation - based on the measurements that bounce back off the item being ultrasounded be that a kidney, bloodflow or a baby. The images are an exact representation of what the ultrasound wave bounced off not an average or range in the same way that percentile graphs are.
Hubby indicated that the best analogy for how an ultrasound image was produced was a photograph. The only difference being that normal photography uses light waves while ultrasound uses ultrasound waves. They are all the forms of energy just osillating at different frequencies and thus the energy's ability to penetrate and the output as visualised by the human eye differs. What ultrasound scanning does via the computer is allows us to see what ultrasound energy can see that is usually not visible to the human eye.
As for the safety, hubby has indicated this is a very contentious issue in the industry. Whilst there have been no studies that prove that ultrasound is safe - there is nothing but anecdotal evidence and weak correlations that prove it is dangerous. It is a naturally occuring form of energy in our environment - given - not usually at the intensities used in ultrasound scanning. Realistically to choose to or not to have ultrasound - whether for fetal wellbeing or anything else - is just a risk analysis. The only difference between this and other things related to pregnancy and childbirth is that we don't have a specific bad outcome that says its risk percentage is X%.
Using the arguement that it hasn't been proven safe will never work as I am sure that I could also prove using statistics that of all the babies born with Downs Syndrome that 80%+ of their mothers ate potatos or rice - does this then mean that these cause Downs Syndrome or alternatively if you eat these you have a X% risk of Downs Syndrome. Until we have a specific outcome that can be proven to be caused by ultrasound, whilst eliminating other possible causes, we have no choice but to assume it is safe - if we don't then women should also be counselled against a myriad of other normal life activities that have at one time or another been questioned for links to medical problems (I remember computers and photocopier radiation to unborn babies being an issue in the early 80s).
By all means exercise caution and do not recommend unnecessary procedures but don't scare women of possible consequences when no such consequences have ever been proven. Women get enough fear instilled in them from the obstetricians.
Far more valuable is to spend time educating women of the ones we know are dangerous with proven risks like drugs in pregnancy and unnecessary caesarean sections.
Debby
